Add support for a "utf-8" mode

NOTE! MicroEmacs is very much a byte-based editor, and the new utf-8
support is purely an issue of terminal input and output.  The file
contents themselves are in the 8-bit space.  In that space, Unicode is
the same as Latin1.

The new mode is called "utf-8", and is enabled automatically by the
new emacs.rc when $LANG contains the substring "UTF-8".

I'm sure people would like to some day also edit real UTF-8 contents,
rather than just edit old 8-bit Latin1 contents in a UTF-8 terminal.
However, that's an independent (and much bigger and thornier) issue.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

estruct.h

@@ -493,7 +493,7 @@ typedef struct BUFFER {
 #define	BFTRUNC	0x04		/* buffer was truncated when read */
 
 /*	mode flags	*/
-#define	NUMMODES	9	/* # of defined modes           */
+#define	NUMMODES	10	/* # of defined modes           */
 
 #define	MDWRAP	0x0001		/* word wrap                    */
 #define	MDCMOD	0x0002		/* C indentation and fence match */
@@ -504,6 +504,7 @@ typedef struct BUFFER {
 #define MDMAGIC	0x0040		/* regular expresions in search */
 #define	MDCRYPT	0x0080		/* encrytion mode active        */
 #define	MDASAVE	0x0100		/* auto-save mode               */
+#define MDUTF8  0x0200		/* UTF-8 input/output mode      */
 
 /*
  * The starting position of a region, and the size of the region in