Often Perl modules are written to wrap functionality 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.

It may also be necessary to search for the correct library to link against, or
for the right include directories to find header files in. This class also
provides assistance here.