Improve Compass window butmap caching logic.
Improve quilt performance by deferring all region calculations until just-in-time.
Improve OpenGL performance by avoiding GL attribute push/pop where possible.
Correct build error on previous but 1 commit.
Improve math (int)round() function performance in S57 module.
Merge branch 'master' into refactoring

Conflicts:
	include/Quilt.h
	include/cutil.h
	include/ocpn_types.h
	src/Quilt.cpp
	src/chart1.cpp
	src/chcanv.cpp
	src/ocpndc.cpp
	src/s52plib.cpp