Updated version number on main page.
Removed C99-ism for the sake of OS X 10.6.

Fixes #241.
Added background colour for non-table and non-note <code> elements.
Removed <code> element background from other undesirable cases.
Added credit.
Fixed constness of function parameters.
Fixed refresh of debug context attribute.
Fixed documentation copypaste error.
Made GLX 1.3 the minimum supported version.
Made use of Win32 W-suffixed symbols explicit.
Further separation of window and context.

The context related parts of _GLFWwndconfig have been moved to
_GLFWctxconfig and given better names.  Window hint and attribute
members have been renamed to match.
Added missing link flags for threaded example.
Moved some VC++ specific hacks to platform header.
Added missing suffix for WNDCLASSW.
Fixes for legacy MinGW 4.2.
Removed stale comment.
Fixed link flags for threaded example.
Updated broken RandR gamma comment.
Added caching of X11 NULL atom.
Fixed missing ICCCM protocol message checks.