Fix ocl::pyrUp
Use predefined OpenCL function to convert integers to floating points.
This is more accurate than before as it enables:
1. saturate cast
2. customized rounding
Merge branch '2.4' of https://github.com/Itseez/opencv into 2.4_pyrup_fix
Clean up spaces in ocl.hpp
Add BFMatcher_OCL class alias for BruteForceMatcher_OCL.
This adds a similar interface with pure-cpp and gpu versions.
Merge pull request #884 from pengx17:2.4_pyrup_fix
Merge pull request #885 from pengx17:2.4_bfmatcher_ocl