Do not let TexureMapper create backing stores that are too large

TextureMapper without Coordinated Graphics will preallocate all tiles
for a backing store. This makes it impossible to handle very large
backing stores as they will cause memory exhaution.

This patch disables composited layers with more pixels than 8192
squared, unless the ChromeClient has allowed large accelerated
layers.

Task-number: QTBUG-41404
Change-Id: Id71628da139f886aceb00732ae59dac2600ef863
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Load flags used by Qt modules when compile testing for a module

In order to pick-up the include path and library path passed
to Qt configure, the configure tests needs to load the Qt
build config.

Change-Id: I881d5e87a08bf8dab5058802dc80ca58d0eed5b1
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>