libc: regex: retire internal EMPTBR ("Empty branch present")

It was realized just a little too late that this was a hack that belonged in
individual regex(3)-using applications. It was surrounded in NOTYET and not
implemented in the engine, so remove it.

lib/libc/regex/regcomp.c

@@ -691,15 +691,9 @@ static bool
 p_branch_empty(struct parse *p, struct branchc *bc)
 {
 
-#if defined(LIBREGEX) && defined(NOTYET)
-	if (bc->outer)
-		p->g->iflags |= EMPTBR;
-	return (true);
-#else
 	(void)bc;
 	SETERROR(REG_EMPTY);
 	return (false);
-#endif
 }
 
 /*

lib/libc/regex/regex2.h

@@ -186,7 +186,6 @@ struct re_guts {
 #		define	USEBOL	01	/* used ^ */
 #		define	USEEOL	02	/* used $ */
 #		define	BAD	04	/* something wrong */
-#		define	EMPTBR	010	/* empty branch present */
 	int nbol;		/* number of ^ used */
 	int neol;		/* number of $ used */
 	char *must;		/* match must contain this string */