[jitter] ANN: jit.gl.lua beta4

I've just uploaded a new beta for jit.gl.lua to my share page on
cycing74.com.  The list of changes is roughly

- new jit.gl.draw_begin / jit.gl.draw_end methods for setting opengl
state based on the settings of a jit.gl object independent of whether
that object actually draws anything (see test.ob3d.lua in the
examples)
- new last_inlet attribute for querying which inlet the last message
came through
- fix for non-existant outlet crash
- methods called from patcher no longer defer-low

enjoint,
wes