widl: Cast-qual warning fix

[Andrew Talbot]

Changelog:
    widl: Cast-qual warning fix.

diff -urN a/tools/widl/parser.l b/tools/widl/parser.l
--- a/tools/widl/parser.l	2006-09-14 17:51:58.000000000 +0100
+++ b/tools/widl/parser.l	2006-10-10 16:22:19.000000000 +0100
@@ -337,7 +337,7 @@
 	}
 #endif
 	if (kwp) {
-		parser_lval.str = (char*)kwp->kw;
+		parser_lval.str = xstrdup(kwp->kw);
 		return kwp->token;
 	}
 	parser_lval.str = xstrdup(kw);