Fix fillRect on RGBA8888 images

The fill color was not correctly converted before being filled into
RGBA8888 images. This patch adds a function with convertion and
adds tests for it to tst_qpainter.

Change-Id: If8b0e6db38b2794a60301842e25f377eb7216796
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
Uic: remove unused option -3

Change-Id: I2ded3a3c90eea0ae37619ff39a8111a589c4573b
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Avoided zero devision in cube root approximation

Halley's method to get a better approximation is omitted, if it
would include a devision by zero (INFINITY/NaN is worse).

Change-Id: Ida09326e2b5892d7cb21bcb956631c289e5b56ba
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
iOS: Move platform plugin linking logic into iOS-specific qt.prf

Change-Id: I54350c8df3fe4bf20fc59cd42a28458018664eef
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>