widl: Write-strings warnings fix

[Andrew Talbot]

Changelog:
    widl: Write-strings warnings fix.

diff -urN a/tools/widl/widltypes.h b/tools/widl/widltypes.h
--- a/tools/widl/widltypes.h	2006-06-02 17:20:03.000000000 +0100
+++ b/tools/widl/widltypes.h	2006-06-23 21:32:36.000000000 +0100
@@ -198,7 +198,7 @@
 };
 
 struct _type_t {
-  char *name;
+  const char *name;
   unsigned char type;
   struct _type_t *ref;
   const attr_t *attrs;