specs: Improve wglChoosePixelFormat{ARB,EXT} description.

WGL_EXT_pixel_format's spec states that the returned nNumFormats value
may be larger than nMaxFormats.  WGL_ARB_pixel_format states that the
returned nNumFormats value is guaranteed to be no larger than
nMaxFormats, but many implementations don't obey this regardless.
gltrace: Fix false warnings about glArrayElement.

Only warn if glArrayElement is actually called.