opengl.gl: Fix opengl loading for Windows.
io.encodings: Add a stream-tell method for decoder streams.
unix.utmpx: Support utmpx on linux and fix on macosx. Add a unit test.
unix.utmpx: Fix bootstrap on linux, add platform-specific structs.
FUEL: unmask `fuel-refresh-all`

`fuel-refresh-all` is documented as mapped onto "\C-c\C-r", but this was
masked by an undocumented mapping for `fuel-eval-region` (which is
already bound to "\C-c\C-e\C-r").