Fix text drawing function, and a few cosmetic changes

The text drawing function for both OpenGL and OpenGL-ES 2.0 is
finally fixed by correcting a major bug in the code that updates
the colors for the text drawing functions.

Cosmetic changes and additions to the README and other source
file comments.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>
Re-enable moving balls in demo8

Re-enable the automatically moving but physics-governed balls
in demo8 and add the missing emission texture used for half of
them.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>