libc/regex: constify more data

[Miod Vallat]

The following diff constifies the strings in cnames[]. No functional
change.

Index: cname.h
===================================================================
RCS file: /OpenBSD/src/lib/libc/regex/cname.h,v
retrieving revision 1.5
diff -u -p -r1.5 cname.h
--- cname.h     2 Jun 2003 20:18:36 -0000       1.5
+++ cname.h     29 Dec 2020 09:30:53 -0000
@@ -36,8 +36,8 @@
  */
 
 /* character-name table */
-static struct cname {
-       char *name;
+static const struct cname {
+       const char *name;
        char code;
 } cnames[] = {
        { "NUL",                        '\0' },
Index: regcomp.c
===================================================================
RCS file: /OpenBSD/src/lib/libc/regex/regcomp.c,v
retrieving revision 1.35
diff -u -p -r1.35 regcomp.c
--- regcomp.c   13 Oct 2020 04:42:28 -0000      1.35
+++ regcomp.c   29 Dec 2020 09:30:53 -0000
@@ -826,7 +815,7 @@ p_b_coll_elem(struct parse *p,
     int endc)                  /* name ended by endc,']' */
 {
        char *sp = p->next;
-       struct cname *cp;
+       const struct cname *cp;
        size_t len;
 
        while (MORE() && !SEETWO(endc, ']'))