Add extensions:
===============

1. Add appropriate definitions for new extension in nffile.h
2. Update extension_descriptor array in nfx.c to reflect the new extension.
   Increase user index ( 3rd value )
3. Add filter in grammar.y
4. test filter with nftest.
5. nffile_inline.c
6. nf_common.c define printing functions
7. nfsta.c add stat definitions