Have the Makefile detect if the CPython-extension build step failed

Also make a note that the CPython development headers are necessary
for running the tests.

docs/INSTALLING.md

-Pyston currently only supports installing from source; the following instructions have fairly tested on Ubuntu, somewhat tested as working on other *nix-y platforms, and are extensively verified as not working on Mac.  (Please see issue #165 for discussion on enabling OSX support, which is pretty difficult.)
+Pyston currently only supports installing from source; the following instructions have fairly tested as working on Ubuntu, and are extensively verified as not working on Mac.  (Please see issue #165 for discussion on enabling OSX support, which is pretty difficult.)
 
 The build instructions assume that you will put the Pyston source code in `~/pyston` and put the dependencies in `~/pyston_deps`.  Barring any bugs, you should be free to put them anywhere you'd like, though the instructions in this file would have to be altered before following.  Also, if you want to change the dependency dir, you'll have to change the value of the the `DEPS_DIR` variable in `src/Makefile`.
 
@@ -112,51 +112,14 @@ sudo apt-get install libgmp3-dev
 
 There are a number of optional dependencies that the build system knows about, but aren't strictly necessary for building and running Pyston.  Most of them are related to developing and debugging:
 
-### valgrind
-
-Since Pyston uses a custom memory allocator, it makes use of the valgrind client hooks to help valgrind understand it.  This means that you'll need a copy of the valgrind includes around; I also suggest that if you want to use valgrind, you use a recent version since there are some instructions that LLVM emits that somewhat-recent versions of valgrind don't understand.
-
-To install:
-
-```
-cd ~/pyston_deps
-sudo apt-get install liblzma-dev
-wget http://valgrind.org/downloads/valgrind-3.9.0.tar.bz2
-tar xvf valgrind-3.9.0.tar.bz2
-mkdir valgrind-3.9.0-install
-cd valgrind-3.9.0
-./configure --prefix=$HOME/pyston_deps/valgrind-3.9.0-install
-make -j4
-make install
-sudo apt-get install libc6-dbg
-cd ~/pyston/src
-echo "ENABLE_VALGRIND := 1" >> Makefile.local
-```
-
-### Debug build of libunwind
-
-Assuming you've already built the normal version above:
-
-```
-cd ~/pyston_deps
-cp -rv libunwind-trunk libunwind-trunk-debug
-mkdir libunwind-trunk-debug-install
-cd libunwind-trunk-debug
-CFLAGS="-g -O0" CXXFLAGS="-g -O0" ./configure --prefix=$HOME/pyston_deps/libunwind-trunk-debug-install --enable-shared=0 --enable-debug --enable-debug-frame
-make -j4
-make install
-echo "USE_DEBUG_LIBUNWIND := 1" >> ~/pyston/src/Makefile.local
-```
+### CPython headers
 
-This will link pyston_dbg and pyston_debug against the debug version of libunwind (the release pyston build will still link against the release libunwind); to enable debug output, set the UNW_DEBUG_LEVEL environment variable, ex to 13.
+We have some extension module tests, in which we compile the extension module code for both Pyston and CPython.
 
-### distcc
 ```
-sudo apt-get install distcc distcc-pump
+sudo apt-get install python-dev
 ```
 
-You can then use distcc by doing `make USE_DISTCC=1`
-
 ### gtest
 
 For running the unittests:
@@ -189,12 +152,6 @@ TODO: GDB should be able to determine its data directory.  maybe it should be in
 from inside the source dir?
 --->
 
-### gperftools (-lprofiler)
-```
-download from http://code.google.com/p/gperftools/downloads/list
-standard ./configure, make, make install
-```
-
 ### gold
 
 gold is highly recommended as a faster linker, and Pyston contains build-system support for automatically using gold if available.  gold may already be installed on your system; you can check by typing `which gold`.  If it's not installed already:
@@ -219,6 +176,61 @@ sudo apt-get install linux-tools-`uname -r`
 # may need to strip off the -generic from that last one
 ```
 
+### distcc
+```
+sudo apt-get install distcc distcc-pump
+```
+
+You can then use distcc by doing `make USE_DISTCC=1`
+
+# Misc tools
+
+These are only useful in specific development situations:
+
+### valgrind
+
+Since Pyston uses a custom memory allocator, it makes use of the valgrind client hooks to help valgrind understand it.  This means that you'll need a copy of the valgrind includes around; I also suggest that if you want to use valgrind, you use a recent version since there are some instructions that LLVM emits that somewhat-recent versions of valgrind don't understand.
+
+To install:
+
+```
+cd ~/pyston_deps
+sudo apt-get install liblzma-dev
+wget http://valgrind.org/downloads/valgrind-3.9.0.tar.bz2
+tar xvf valgrind-3.9.0.tar.bz2
+mkdir valgrind-3.9.0-install
+cd valgrind-3.9.0
+./configure --prefix=$HOME/pyston_deps/valgrind-3.9.0-install
+make -j4
+make install
+sudo apt-get install libc6-dbg
+cd ~/pyston/src
+echo "ENABLE_VALGRIND := 1" >> Makefile.local
+```
+
+### Debug build of libunwind
+
+Assuming you've already built the normal version above:
+
+```
+cd ~/pyston_deps
+cp -rv libunwind-trunk libunwind-trunk-debug
+mkdir libunwind-trunk-debug-install
+cd libunwind-trunk-debug
+CFLAGS="-g -O0" CXXFLAGS="-g -O0" ./configure --prefix=$HOME/pyston_deps/libunwind-trunk-debug-install --enable-shared=0 --enable-debug --enable-debug-frame
+make -j4
+make install
+echo "USE_DEBUG_LIBUNWIND := 1" >> ~/pyston/src/Makefile.local
+```
+
+This will link pyston_dbg and pyston_debug against the debug version of libunwind (the release pyston build will still link against the release libunwind); to enable debug output, set the UNW_DEBUG_LEVEL environment variable, ex to 13.
+
+### gperftools (-lprofiler)
+```
+download from http://code.google.com/p/gperftools/downloads/list
+standard ./configure, make, make install
+```
+
 ### ninja-based LLVM build
 
 Ninja is supposed to be faster than make; I've only tried it very briefly, and it does seem to be faster when modifying LLVM files.  May or may not be worth using; thought I'd jot down my notes though:

src/Makefile

@@ -910,7 +910,7 @@ ext_pyston: $(TEST_EXT_MODULE_NAMES:%=../test/test_extension/%.pyston.so)
 
 .PHONY: ext_python
 ext_python: $(TEST_EXT_MODULE_NAMES:%=../test/test_extension/*.c)
-	cd ../test/test_extension; python setup.py build; cd -
+	cd ../test/test_extension; python setup.py build
 
 $(FROM_CPYTHON_SRCS:.c=.o): %.o: %.c $(BUILD_SYSTEM_DEPS)
 	$(ECHO) Compiling C file to $@