warnings: fix early exit of warnings treated as errors

Treating warnings as errors caused Bison to exit earlier than needed, making it
hide warnings that would have been printed had -Werror not been set.

Also, fix a bug that caused some context information of errors to not be
shown.

* src/complain.c (complaint_issued): Rename as...
(complaint_status): This, and change its type from boolean to
* src/complain.h (err_status): This, new enumeration.
* src/main.c (main): Adjust (only finish early if an actual complaint was
risen, not a mere warning treated an error).
* src/reader.c: Adjust.

src/complain.h

@@ -70,7 +70,18 @@ void complain_indent (location const *loc, warnings flags, unsigned *indent,
                       char const *message, ...)
   __attribute__ ((__format__ (__printf__, 4, 5)));
 
+
+/** Warnings treated as errors shouldn't stop the execution as regular errors
+    should (because due to their nature, it is safe to go on). Thus, there are
+    three possible execution statuses.  */
+typedef enum
+  {
+    status_none,
+    status_warning_as_error,
+    status_complaint
+  } err_status;
+
 /** Whether an error was reported.  */
-extern bool complaint_issued;
+extern err_status complaint_status;
 
 #endif /* !COMPLAIN_H_ */