Fix aliasing issues when compiler with non g++ makespecs

As it turns out, need -fno-strict-aliasing. It should not only be applied when
the mkspec happens to have g++ in its name, we also need it for qnx (qcc) and
any other compiler that pretends to be gcc (sets QMAKE_COMPILER to gcc).

Change-Id: Id4d152e4fcaa06ecd8acb47a3d8a41997ba82b75
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>
Fix clang C++11 build

clang with "-std=c++11" does not allow implicit conversion from false
to null pointer.
Although clang with C++03 and gcc with C++03/11 treat it as warning,
not error, the conversion was in fact invalid.

Change-Id: I92629f9e313d0a00c4d39ce2e539ed140707ad5c
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@theqtcompany.com>
Bump version

Change-Id: I2bc053c14e8b1684cdab81d31ba30b66afd2b97a
Merge remote-tracking branch 'origin/5.4.0' into 5.4

Change-Id: Ia7239e9362ee936303aaa084cba0fd67c5576c48
Merge remote-tracking branch 'origin/5.4' into dev

Conflicts:
	.qmake.conf

Change-Id: Ib2bcdfc23e0e8274e8cc43ed34ec34b1e0cb986d