make some arrays const

this way they'll go into .rodata, decreasing memory pressure.

src/ctype/iswalpha.c

@@ -1,6 +1,6 @@
 #include <wctype.h>
 
-static unsigned char table[] = {
+static const unsigned char table[] = {
 #include "alpha.h"
 };
 

src/ctype/iswpunct.c

@@ -1,6 +1,6 @@
 #include <wctype.h>
 
-static unsigned char table[] = {
+static const unsigned char table[] = {
 #include "punct.h"
 };
 

src/ctype/wcwidth.c

@@ -1,10 +1,10 @@
 #include <wchar.h>
 
-static unsigned char table[] = {
+static const unsigned char table[] = {
 #include "nonspacing.h"
 };
 
-static unsigned char wtable[] = {
+static const unsigned char wtable[] = {
 #include "wide.h"
 };