Add tests for the use of ParseRegExp.pm.

           'USING' now takes either a string or array reference as its value (as
           does the Inline::C equivalent).

           'LIBS' and 'TYPEMAPS' can now optionally be assigned as a (space
           delimited) string or an array reference (same as 'INC'). Previously
           'LIBS' and 'TYPEMAPS' had to be assigned as an array reference.

           'INC' (in the generated Makefile.PL) no longer automatically includes the cwd.

           'TYPEMAPS' (in the generated Makefile.PL) no longer automatically specifies
           the standard perl typemap. (Doing so was annoying and, afaict, unnecessary.)

Add C2XS-Cookbook.pod

Minor correction to WRITE_PM

           The C source code can now be alternatively provided by either a 
           'CODE' or 'SRC_LOCATION' key. 

Can now write a .pm file for you as well

           Check that only valid config options have been passed via the "config
           options" argument.
       
           Catch the error (and die) if a non-existent typemap is specified
           in the TYPEMAPS config option.

           If the specified build_dir does not exist, die(). Previously, a warning
           was issued and the files written to the current working directory.