added checksum of the file. Now we have size + magic string + checksum
to detect that all is ok.
Plus misc fixes for "make dist" to work and the resulting tarball to build


include/Makefile.am:
  adding pagecache.h to help the tarball build.
  The model of pagecache.h, keycache.h, is in pkginclude_HEADERS,
  wonder why. Adding pagecache.h to noinst_HEADERS for now.
storage/maria/Makefile.am:
  adding ma_control_file.h to help the tarball build
storage/maria/ma_control_file.c:
  adding a simple checksum to the control file.
  We protect against corruption of this file like this:
  - test size
  - test magic string at start
  - test checksum
  I also add some simple my_message() errors (to be changed to a better
  reporting later).
storage/maria/ma_control_file.h:
  comments
storage/maria/ma_control_file_test.c:
  test of wrong checksum in control file
storage/maria/CMakeLists.txt:
  just to make "make dist" happy for now.