In "FreeBSD": "-I" belongs to CPPFLAGS, not CFLAGS
Use POSIX grep syntax
Removed "-Wno-deprecated" from COMPILE_FLAGS

This feature is new to GCC 4.4, while OpenBSD uses 4.2.1
Ignore files, generated by "configure" script
Don't tracked Makefile and config.h

Both files are generated by ``configure'' script. Given that they:

  1. may change after running ``configure'' and
  2. are setup-dependent

there's no need to track them anyway.