Enhance msaa and blitframebuffer on ES with vendor extensions

The support already in place for ANGLE is now extended for NV.

On ES 2.0 the only way to get multisampled renderbuffers and blitframebuffer
is through vendor-specific extensions. QOpenGLFunctions is updated to resolve
the related functions for both ANGLE and NV, in addition to EXT.

Task-number: QTBUG-39187
Change-Id: I1aab805ced3d06dde3dc547221bbf833ff8e06c2
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Support framebuffer blit and msaa without extensions on GLES3

Call the standard functions directly in GLES 3.0+ builds.

The catch here, just like with the mapBuffer changes, is that we could,
in theory, dynamically load a GLES3 implementation on the !QT_OPENGL_ES_3
path too. However this is limited to Windows currently and we don't have
a full GLES3 stack there (yet), and even when we do get it, the ANGLE
extensions for blit and multisampling will still work. Therefore this
isn't really an issue for now.

Task-number: QTBUG-38168
Task-number: QTBUG-39187
Change-Id: I343a737218c9fe438ee1603b37e93f0400d952a5
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Support translucent windows on eglfs

Task-number: QTBUG-39834
Change-Id: I3f6b041c992365d611aa97a41bc37e80b764b78a
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Emit a notifications when childMode, initial and errorState are changed.

In order to properly use QState object in QML we need to know when these
properties are changed.

Change-Id: I37f8295e5201686a52d448cc42db331a8f8e792f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: BogDan Vatra <bogdan@kde.org>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
Emit a notifications when defaultState and historyType are changed.

In order to properly use QHistoryState object in QML we need to know
when these properties are changed.

Change-Id: I28c783436410c84bc64a919ac18c183f7a5eb9ad
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Volker Krause <volker.krause@kdab.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>