Fixing a few nits

Hi Tim,

I've made a few changes to NYTProf to clean up a few things.
- running "perl Makefile.PL" warned about missing files.  Since most of these files are generated by running "perl Makefile.PL", I removed them from MANIFEST.  Also, the MANIFEST has README, but not the README.md in the MANIFEST, so I fixes that.
- silenced several warnings in NYTProf.xs generated with my higher level of gcc warnings
- added a few extra files to .gitignore (.c's, .o's, a .bs and a test output file)

Steve