avoid making AIS theta calculations if they are immediately discarded
refactor ais drawing code from chcanv.cpp to ais.cpp
simplify ais rendering logic, and reduce redundant calculations
programatically support n-bells eliminating 3-8bells.wav thus reducing package size
Merge branch 'master' of https://github.com/OpenCPN/OpenCPN into reduced-bells
use wxDC#IsOk instead of (at least in wxwidget3.0 non-existent) wxDC#Ok
Fix int->void* conversion that is invalid for 64bit systems
Merge pull request #146 from seandepagnier/reduced-bells

Reduced bells
Merge pull request #147 from seandepagnier/ais_optimizations

AIS optimizations
Merge pull request #148 from nkiesel/master

use wxDC#IsOk instead of (at least in wxwidget3.0 non-existent) wxDC#Ok
Correct OpenGL symbol texture loading logic
Improve performance of OpenGL raster symbol rendering
Improve OpenGL setup log messages.