(generate_h): cast when calling is* to get rid of a warning

git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@5533 ec53bebd-3082-4978-b11e-865c3cabbd6b

lib/com_err/compile_et.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998 Kungliga Tekniska H<>gskolan
+ * Copyright (c) 1998, 1999 Kungliga Tekniska H<>gskolan
  * (Royal Institute of Technology, Stockholm, Sweden). 
  * All rights reserved. 
  *
@@ -135,7 +135,7 @@ generate_h(void)
 
     snprintf(fn, sizeof(fn), "__%s__", hfn);
     for(p = fn; *p; p++)
-	if(!isalnum(*p))
+	if(!isalnum((unsigned char)*p))
 	    *p = '_';
     
     fprintf(h_file, "/* Generated from %s */\n", filename);