We don't use -Wcast-align ourselves, but the headers trigger warnings
for those users who do, which is not nice.

It increases performance on some devices like Nexus4.
Target Android SDK version increased up to 14.

They're unsequenced if CV_IMIN3 or CV_IMAX3 are invoked more than once
in a single expression.

begin_x[1] is not the second component of the element, but the element
after the one pointed to begin_x. When begin_x points to the last
element, that line overwrites data past the end of the allocation, which,
during my tests, happened to contain the reference count for the matrix.
Hilarity ensues.