remove initial 'calling external C functions' tutorial - it's broken beyond repair

src/tutorial/external.rst

-Calling external C functions
-============================
-
-It is perfectly OK do ``from math import sin`` to use Python's
-``sin()`` function.  However, calling C's own ``sin()`` function is
-substantially faster, especially in tight loops.  It can be declared
-and used in Cython as follows::
-
-  cdef extern from "math.h":
-      double sin(double)
-
-  cdef double f(double x):
-      return sin(x*x)
-
-At this point there are no longer any Python wrapper objects around
-our values inside of the main for loop, and so we get an impressive
-speedup to 219 times the speed of Python.
-
-Note that the above code re-declares the function from ``math.h`` to
-make it available to Cython code.  The C compiler will see the
-original declaration in ``math.h`` at compile time, but Cython
-does not parse "math.h" and requires a separate definition.
-
-When calling C functions, one must take care to link in the appropriate
-libraries. This can be platform-specific; the below example works on Linux
-and Mac OS X::
-
-  from distutils.core import setup
-  from distutils.extension import Extension
-  from Cython.Distutils import build_ext
-
-  ext_modules=[ 
-      Extension("demo",
-                ["demo.pyx"], 
-                libraries=["m"]) # Unix-like specific
-  ]
-
-  setup(
-    name = "Demos",
-    cmdclass = {"build_ext": build_ext},
-    ext_modules = ext_modules
-  )
-
-If one uses the Sage notebook to compile Cython code, one can use a special
-comment to tell Sage to link in libraries::
-
-  #clib: m
-
-Just like the ``sin()`` function from the math library, it is possible
-to declare and call into any C library as long as the module that
-Cython generates is properly linked against the shared or static
-library.

src/tutorial/index.rst

@@ -4,7 +4,6 @@ Tutorials
 .. toctree::
    :maxdepth: 2
 
-   external
    clibraries
    cdef_classes
    pxd_files