Often Perl modules are written to wrap functionallity found in existing
C headers, libraries, or to use OS-specific features. It is useful in
the Build.PL or Makefile.PL file to check for the existance of these
requirements before attempting to actually build the module.

Objects in this class provide an extension around ExtUtils::CBuilder to
simplify the creation of a .c file, compiling, linking and running it,
to test if a certain feature is present.
