Fix potential OOB in Windows Dedicated TTY CON_Show

Found by Coverity.
OpenGL2: Reimplement MD3 tangent space calculation.
OpenGL2: Really obvious optimization to previous commit.
Merge remote-tracking branch 'ioquake3/master'

Duplicated MD3 changes for MDC (with no changes from MD3 code).

Conflicts:
	code/renderergl2/tr_local.h