opencl: make a few numerical constants more well-behaving on Mac OpenCL

seems that the OSX opencl compiler (Apple's own, not the NVIDIA or AMD one) has
an issue with certain valid but uncommon float constants like "1.f".
(cherry picked from commit 444fd4ad756870b5617b0591266c06d8016ba0ca)

Conflicts:
	data/kernels/denoiseprofile.cl
opencl: workaround for compiler bug in Apple opencl implementation

Apple's implementation fails during init of private filter array. we use global
of a 2D filter array, initialized from host instead. slightly slows down processing on very
fast devices (HD7950) but speeds up processing on some others (GTS450)
(cherry picked from commit 9e4ed3b4e6b81f922fd444facbdafdfc45b619af)

Conflicts:
	data/kernels/denoiseprofile.cl
	src/iop/denoiseprofile.c