[ATCH 0/5] GLX context tag reimplementation

[Adam Jackson]

GLX, apparently as some sort of elaborate prank, has both context IDs and
context tags.  These are _almost_ identical; the functional difference is
that you're allowed to continue to mention the tag of a deleted context
as long as it's still your current context.

The sample implementation of tags has a difficult time with context
lifetime, because we have to keep track of things in two places and be
sure we're not freeing things before we mean to be and blah blah
unmanaged runtimes sure do suck.  But fortunately there's a simpler
implementation that I believe to be within the letter of the law, which
is what the first patch in this series is.

The rest is merely cleanup.

- ajax