gui: Fix erasing elements from list during iteration.

Fixes issue apitrace#357.

gltrace: Fix PBO unpacking on core contexts.

gltrace::PROFILE_COMPAT was a misnomer -- it actually meant desktop
profile.  So b0c5972 broke PBO for core
contexts.

docs: Update news.

Tag a new release 5.0.

There are still many outstanding patches / pull requests that deserve to
be in this release.  But instead of delaying a release any further, I'll
simply make a new minor release when I get around to go through these.

Fixes issue apitrace#239.

Tag a new release 4.0.

Mostly for the benefit of those who prefer a tagged release instead of
master.

Anyway, it has been too long since the last one.  The output of
`git shortlog..HEAD` was impressive.  Thanks to all of them who
contributed.

Fix typo in NEWS.

Rebrand as version 2.0

Describe glretrace -db and --help options; and how to start the GUI.