search distributions for C and XS files by MIME type

removed the ppport.h search

credit to @rwstauner via <https://github.com/Perl-XS/notes/pull/3#issuecomment-30809835>
bump the size of MetaCPAN query to 4000

in order to find all the distributions that contain C code
Merge pull request #4 from zmughal/search-cpan

search distributions for C and XS files by MIME type