drawing sequence basepairs.

drawing sequence basepairs.
OpenGL is not very text friendly. But I can draw AGCTs with something
that's vaguely readable. I tried to use FTGL (a freetype based GL font
rendering library, but I couldn't get it to control the width of fonts
and so they ended up rendering on top of each other.) I used an example
out of the opengl redbook, to hand code glyphs that are at least passable.

The current block of code manages to turn on text rendering only when there's
enough space to make them legible. However I'm not completely convinced that
the text is actually in the right place.

There's also a problem with the python to C++ interface that I worked around
if you create a Sequence object and point a GlSequence to it, if the
python copy goes away, the copy in GlSequence dies, which makes rendering
sequence data a bit challenging.