Update README.md

A trace file can be passed to vogleditor on the command line to have it loaded automatically.
Update qtcreator.md

Add information about launching and debugging projects from within QtCreator since the default Run configuration is not valid.
Fixing issue #32.
Added a check of SDL_GLContext;

src/gltests/include/testcommon.h:
  (1) added assert header when enabling debugging (check is on NDEBUG not being defined);

src/gltests/core-vao/main.c
src/gltests/fixedfunc-multitexcoord-2d/main.c
src/gltests/msaa_depthstencil/main.c
src/gltests/texture-array-1d/main.c
src/gltests/texture-array-2d-msaa/main.c
src/gltests/texture-array-2d/main.c
src/gltests/texture-array-nonzerobase/main.c
src/gltests/texture-array-subimages/main.c
src/gltests/texture-nonzerobase/main.c
  (1) added an assert on the SDL_GLContext being valid;
      why: Open source drivers currently support up to specific OpenGL context
           - so fail early (in order to avoid failure later in the code);
Removing NDEBUG checks;
Merge pull request #35 from kingtaurus/master

Proposed changes to fix issue #32
Merge pull request #2 from ValveSoftware/master

Merge upstream