.gitignore: Remove build products from list

.gitignore: Remove build products from list

The following patterns were previously active.
They have been commented out because the system "make" will pick up build
products in the source tree causing strange build failures.  The benefit
of avoiding an accidental commit of a binary is quickly offset by the
liability of chasing build failures caused by "invisible" files.  This
has burned a few people already and even the source of bug reports.

*.[psS]o
!/contrib/nvi/docs/USD.doc/vi.ref/index.so
!/contrib/nvi/docs/USD.doc/vi.ref/ref.so
*.a
!/bin/csh/USD.doc/csh.a
*.o