wrc: Declare some variables static const

[Andrew Talbot]

Changelog:
    wrc: Declare some variables static const.

diff -urN a/tools/wrc/readres.c b/tools/wrc/readres.c
--- a/tools/wrc/readres.c	2006-05-23 13:49:40.000000000 +0100
+++ b/tools/wrc/readres.c	2007-01-01 13:03:04.000000000 +0000
@@ -32,7 +32,7 @@
 #include "utils.h"
 #include "genres.h"
 
-struct resheader32 {
+static const struct resheader32 {
 	DWORD	ressize;	/* 0 */
 	DWORD	hdrsize;	/* 0x20 */
 	WORD	restype1;	/* 0xffff */