Glexcess

This is the GLExcess demo v1.0 by Paolo "Bustard" Martella from
http://glexcess.com ported to OS4/MiniGL by Alex Carmona.

Compilation went pretty smoothly but the resulting binary had a few issues so
I made a few changes:

1) Replaced the buggy command line arguments handling with this template:

glxs WIDTH/N HEIGHT/N DEPTH/N REFRESH/N

The defaults are "640 480 24 60" (640x480 24bit 60Hz)

Specifying no argument or the first 2 arguments will open a window, while if 3
or more arguments are provided it will open in fullscreen mode.

2) I've set the timing steps to 30 by default (change with A/Z keys).

On my A1-XE with Radeon 7500 it results in what looks like a normal pace though
GPU-intensive sequences may still appear a bit slow.

3) To prevent the usual 100% CPU load from GL (which blocks <= 0 pri tasks),
I've inserted a 20 millisecond delay in the rendering loop.