Fix comment for pre-4 GCCs

#if 0 commented text should be C/C++ commented.
This is from Mozilla Bug 488468: qcms build break with pre-4 GCCs.
diff --git a/qcmsint.h b/qcmsint.h
index 0fb02e2..68bbe21 100644
--- a/qcmsint.h
+++ b/qcmsint.h
@@ -86,8 +86,9 @@
 	uint16_t *output_table;
 };
 #if 0
-this is from an intial idea of having the struct correspond to the data in
-the file. I decided that it wasn't a good idea.
+/* this is from an intial idea of having the struct correspond to the data in
+ * the file. I decided that it wasn't a good idea.
+ */
 struct tag_value {
 	uint32_t type;
 	union {