Sync regex code with Tcl 8.5.11.

Sync our regex code with upstream changes since last time we did this,
which was Tcl 8.5.0 (see commit df1e965e).

There are no functional changes here; the main point is just to lay down
a commit-log marker that somebody has looked at this recently, and to do
what we can to keep the two codebases comparable.

src/backend/regex/regc_locale.c

@@ -499,7 +499,7 @@ cclass(struct vars * v,			/* context */
 {
 	size_t		len;
 	struct cvec *cv = NULL;
-	const char **namePtr;
+	const char * const *namePtr;
 	int			i,
 				index;
 
@@ -507,7 +507,7 @@ cclass(struct vars * v,			/* context */
 	 * The following arrays define the valid character class names.
 	 */
 
-	static const char *classNames[] = {
+	static const char * const classNames[] = {
 		"alnum", "alpha", "ascii", "blank", "cntrl", "digit", "graph",
 		"lower", "print", "punct", "space", "upper", "xdigit", NULL
 	};

src/backend/regex/rege_dfa.c

@@ -272,36 +272,35 @@ static struct dfa *
 newdfa(struct vars * v,
 	   struct cnfa * cnfa,
 	   struct colormap * cm,
-	   struct smalldfa * small) /* preallocated space, may be NULL */
+	   struct smalldfa * sml) /* preallocated space, may be NULL */
 {
 	struct dfa *d;
 	size_t		nss = cnfa->nstates * 2;
 	int			wordsper = (cnfa->nstates + UBITS - 1) / UBITS;
-	struct smalldfa *smallwas = small;
+	struct smalldfa *smallwas = sml;
 
 	assert(cnfa != NULL && cnfa->nstates != 0);
 
 	if (nss <= FEWSTATES && cnfa->ncolors <= FEWCOLORS)
 	{
 		assert(wordsper == 1);
-		if (small == NULL)
+		if (sml == NULL)
 		{
-			small = (struct smalldfa *) MALLOC(
-											   sizeof(struct smalldfa));
-			if (small == NULL)
+			sml = (struct smalldfa *) MALLOC(sizeof(struct smalldfa));
+			if (sml == NULL)
 			{
 				ERR(REG_ESPACE);
 				return NULL;
 			}
 		}
-		d = &small->dfa;
-		d->ssets = small->ssets;
-		d->statesarea = small->statesarea;
+		d = &sml->dfa;
+		d->ssets = sml->ssets;
+		d->statesarea = sml->statesarea;
 		d->work = &d->statesarea[nss];
-		d->outsarea = small->outsarea;
-		d->incarea = small->incarea;
+		d->outsarea = sml->outsarea;
+		d->incarea = sml->incarea;
 		d->cptsmalloced = 0;
-		d->mallocarea = (smallwas == NULL) ? (char *) small : NULL;
+		d->mallocarea = (smallwas == NULL) ? (char *) sml : NULL;
 	}
 	else
 	{

src/backend/regex/regexec.c

@@ -141,7 +141,6 @@ static int	dissect(struct vars *, struct subre *, chr *, chr *);
 static int	condissect(struct vars *, struct subre *, chr *, chr *);
 static int	altdissect(struct vars *, struct subre *, chr *, chr *);
 static int	cdissect(struct vars *, struct subre *, chr *, chr *);
-static int	ccaptdissect(struct vars *, struct subre *, chr *, chr *);
 static int	ccondissect(struct vars *, struct subre *, chr *, chr *);
 static int	crevdissect(struct vars *, struct subre *, chr *, chr *);
 static int	cbrdissect(struct vars *, struct subre *, chr *, chr *);
@@ -708,6 +707,8 @@ cdissect(struct vars * v,
 		 chr *begin,			/* beginning of relevant substring */
 		 chr *end)				/* end of same */
 {
+	int			er;
+
 	assert(t != NULL);
 	MDEBUG(("cdissect %ld-%ld %c\n", LOFF(begin), LOFF(end), t->op));
 
@@ -727,31 +728,16 @@ cdissect(struct vars * v,
 			return ccondissect(v, t, begin, end);
 		case '(':				/* capturing */
 			assert(t->left != NULL && t->right == NULL);
-			return ccaptdissect(v, t, begin, end);
+			assert(t->subno > 0);
+			er = cdissect(v, t->left, begin, end);
+			if (er == REG_OKAY)
+				subset(v, t, begin, end);
+			return er;
 		default:
 			return REG_ASSERT;
 	}
 }
 
-/*
- * ccaptdissect - capture subexpression matches (with complications)
- */
-static int						/* regexec return code */
-ccaptdissect(struct vars * v,
-			 struct subre * t,
-			 chr *begin,		/* beginning of relevant substring */
-			 chr *end)			/* end of same */
-{
-	int			er;
-
-	assert(t->subno > 0);
-
-	er = cdissect(v, t->left, begin, end);
-	if (er == REG_OKAY)
-		subset(v, t, begin, end);
-	return er;
-}
-
 /*
  * ccondissect - concatenation subexpression matches (with complications)
  * The retry memory stores the offset of the trial midpoint from begin,