Fix rounding bias in UIView.

This patch set fixes a 'drifting' issue in the autoresizing logic. This behaviour is caused by the rounding bias introduced by the use of `floorf` function in `-[UIView _superviewSizeDidChangeFrom:(CGSize)oldSize to:(CGSize)newSize]`.

It fixes it by keeping an internal CGRect for the UIView's frame using unrounded floats. When updating the internal CGLayer for the view, it rounds it using CGRectIntegral to prevent sub-pixel blurring when the autoresizing puts a view at non-integer coordinates.

It then removes the unnecessary calls to `floorf` in the autoresizing calculations.

Fixes BigZaphod/Chameleon#82.