Retouch stability

1. In two cases OpenCL memory copy/allocation could fail without a returned error code so
   unnoticed and without a CPU fallback.
2, The bilateral and gaussian parts were not checked for errors so possibly unnoticed wrong
   results without a fallback,

Maintenance:
constified, dont test for deallocation is not necessary, don't report individual allocation
errors as mostly not reported anyway and not informative at all. So reformatting for readability.