- removed procedures program_name, global_c_stmt, entry_code,
  exit_code from parse.c, instead pass results to procedure program
- factorized initial parts of snc.y
- allow global entry/exit only before/after state sets (as stated in docs)

cleanup includes
- unified naming to original underscore convention
- made most things static
- removed many sporadic extern declarations to header files
- moved prototypes in parsedefs.h to parse.h and (new) snc_main.h
- moved definition of expr_count to phase2.c
- removed unused definition of find_state