Add IPP support in cvtColor function
macros -> template in IPP support cvtColor
gpu TVL1 Optical Flow optimization:

do not calculate sum of error in every round of iteration;
instead the error will be summed every 2nd times or more, 
if the previous sum of error is too far away from threshold.
Merge pull request #1346 from jet47:gpu-tvl1-optimization
Restored one executable bit that was lost during the war on whitespace.
appended ocl::finish to test_cycle defines
Merge pull request #1349 from ilya-lavrenov:ocl_perf_finish
Deleted the now-empty ocl perf_precomp.cpp.

See pull request #1241 for why.
Merge pull request #1213 from kdrobnyh:color
Merge pull request #1357 from SpecLad:less-precomps
LibTIFF Win32 API back-end disabled for Windows RT.