common.c:	public functions for both the backend and the frontend.
		requires conv.c and wchar.c
conv.c:		static functions and a public table for code conversion
wchar.c:	mostly static functions and a public table for mb string and
		multi-byte conversion
mbutilc.c:	public functions for the backend only.
		requires conv.c and wchar.c
wstrcmp.c:	strcmp for mb
wstrncmp.c:	strncmp for mb
varable.c:	public functions for show/set/reset variable commands
