Merge pull request #143 from seandepagnier/master

small fixes, mostly to grib plugin
Implement OpenGL VBO support for vector chart AREA object rendering.
Implement OpenGL VBO for cm93 AREA objects
Correct fault on color scheme change while building compressed textures.
Partially revert 4c53eb2b199ce1309473727210240f6ffcd4c3ac
Correct OpenGL special character rendering.
Implement mutex locking of chart database cache.
Correct ENC POINT object text box calculations.
Complete OpenGL VBO implementation
Correct rendering error on color scheme change when using FBO.