Merge pull request #115 from seandepagnier/optimum-merging

Optimum merging -- more incremental changes
Merge pull request #116 from seandepagnier/optimum-merging

Optimum merging -- a few more updates and corrections
3.3.1715
Correct and harmonize raster chart region calculation for skewed charts.
Set OpenGL texture compression options to default "OFF"
corrections to opengl route rendering
Merge branch 'master' of https://github.com/OpenCPN/OpenCPN into optimum-merging