Fixed signed/unsigned comparison
Merge pull request #138 from nkiesel/master

Fixed signed/unsigned comparison
fix interpolation for gribs with negative Dj
fix deadlock for multiple threads testing coastline crossings
Improve cache rebuilt UI elements
Enable higher quality compression when building cacheable raster textures
Correct compressed texture error.
Enables extended instruction set build (/arch:SSE2) on Windows builds.
Fix the install prefix handling to again support Launchpad
Merge branch 'master' of https://github.com/OpenCPN/OpenCPN

Conflicts:
	plugins/grib_pi/src/GribRecord.cpp
	src/chart1.cpp