0028095: Draw Harness, ViewerTest - use RGBA format instead of BGRA within vreadpixel

0028095: Draw Harness, ViewerTest - use RGBA format instead of BGRA within vreadpixel

OpenGl_Workspace::BufferDump() now implicitly converts RGBA dump
into requested BGR, BGRA and RGB image.

DRAW command dversion is improved to report OpenGL variant used (desktop or ES); reporting of version of MSVC is corrected for VC14 and above; reporting of HAVE_OPENCL option is removed.

Usage of command vdump is corrected in some tests to specify extension .png for an image file.

Compiler warning is eliminated in OpenGl_Text.cxx (OpenGL ES mode only).