Added TKOpenGlTest and TKD3DHostTest Draw Harness plugins.
TKOpenGlTest is automatically loaded by ViewerTest::ViewerInit().
Commands vgldebug, vvbo, vcaps and vuserdraw have been moved to TKOpenGlTest.
New command vglshaders lists GLSL programs defined by OpenGl_GraphicDriver,
previously implemented by "vshaderprog -list".
Added new command vdriver for graphic driver selection.
Removed erroneous code from command vstereo.
OpenGl_ShaderManager::pointSpriteAlphaSrc() now does not return alpha from Red channel
for RGBA marker texture in Core profile.
OpenGl_ShaderManager::prepareStdProgramFlat() - restored code for drawing points without texture.
Built-in GLSL programs now flip .y in shaders instead of
relying on GL_POINT_SPRITE_COORD_ORIGIN unavailable on OpenGL ES.
Added sample markers.tcl (moved from test cases).
Sample now includes marker_kr.png for testing marker orientation.
