fixed dropper debug printing
Merge pull request #128 from mniip/dropper-debug

fix dropper debug printing
Merge remote-tracking branch 'upstream/master' into fastrender
Raster drawing uses common get/setpixel methods

Instead of directly accessing the video array in each raster method, use
functions which can be changed once instead of changing each access.
Speed up + clean up rendering

Move OpenGL #ifdefs into their own function, leaving the SDL code much
tidier.
Apply logic to glow and blur rendering to avoid drawing unneeded pixels,
speeding both up by a good margin.
Parallelize render_gravlensing for a much-needed speed up on multi-core
computers.
Faster parts_avg, more efficient SPRK

The parts_avg function is relatively slow thanks to the use of the
floating point position.  The fast_parts_avg function uses integer
positions, making it faster.  Some elements have been changed to use the
new function.
The SPRK element was wasting time computing parts_avg when it didn't
need to.