gui: Allow to edit strings.

Based upon the surrounding code.  There might be a better way to achieve
it, but this seems better than no support.

Issue #159.
Support for Mac OS X 10.5 Leopard

CGLShareGroupObj and IOSurfaceRef were added in 10.6 Snow Leopard SDK
Add workarounds to glimports.hpp to support building for pre-10.6.
glxtrace: Trace GLX_NV_present_video/GLX_NV_video_output/GLX_NV_video_capture calls minimally.
wgltrace: Update wglapi.py from specs.

Via the scripts in the scripts subdir.

Might not be perfect but better than nothing.
d3dstate: Remove spurious statements.
directxtex: Fix assertion failures on MinGW.
d3dstate: Dump compressed D3D10/11 textures.
cli/trim: Fix error message.
cli/sed: Very basic stream editing of traces.

Extremely limited, but have to start from somewhere.
Replace dynamic_cast with virtual functions.

apitrace can be built with without RTTI (runtime type information)
providing that dynamic_cast isn't used.
Aggregate all info on debugging into a single place.