This change applies to all qtbase modules, tools and applications. It
does not apply to examples or unit tests.

This change complements the changes done to mkspecs/qt_common.prf
(especially 043b8091 and
ebfd85a4

). It enables -Werror checking
in qtbase for GCC 4.6-4.8, Apple clang 4.0-4.2 and ICC 13.0-14.0.

Change-Id: I6d29a7a1b3716960a149409f551363385991714c
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>