Create base for Forth interpreter

src/Makefile

src/Sourcefile

src/filesrch.c

src/filesrch.h

src/forth/Sourcefile

src/forth/srbf.h

src/forth/srbf_address.c

src/forth/srbf_context.c

src/forth/srbf_word.c

src/forth_script.c

src/forth_script.h

src/m_menu.c

src/w_wad.c

src/w_wad.h