add accuracy tests while running perf
fix the waring in gemm test
fix a warning
Merge pull request #895 from bitwangyaoyao:2.4_perf
fix parenthesis
Merge commit 'b51a1a7d' (PR #895 from 2.4)

Conflicts:
	modules/ocl/CMakeLists.txt
	modules/ocl/perf/perf_color.cpp
	modules/ocl/perf/perf_match_template.cpp
	modules/ocl/perf/precomp.cpp
	modules/ocl/perf/precomp.hpp
Merge pull request #914 from SpecLad:master
Fix a build error which manifests when building with CUDA < 5.
Merge pull request #917 from SpecLad:cuda-4-build
Merge pull request #911 from jrdi:patch-1