Fix reallocation of D buffer in gemm

Conflicts:
	modules/core/src/matmul.cpp
Merge pull request #3108 from LeszekSwirski:fix-gemm-buf-allocate-2.4
Fixed getConversionInfo() for YUV2RGBA_* conversions
fixing GT and GE comparison symbol
Merge pull request #3118 from akarsakov:fix_cvtcolor_perf
Merge pull request #3120 from StevenPuttemans:fix_bug3863
Fixed range for 'v' channel for 8U images.