slight fix for wx-2.8
Merge pull request #129 from seandepagnier/master

various small bugfixes
Correct wxString initialization of defined parameter PREFIX
Correct outline colour for PlugIn vector charts
Correct for some OpenGL drivers poor smooth line width granularity
Improve cm93 chart scale selection logic to preclude overzoom where possible.
Correct fault on Mac, AISTargetListDialog "Close" button
fix various compiler warnings
Merge branch 'master' of https://github.com/OpenCPN/OpenCPN
Implement user icons with transparent background for OpenGL
Correct OpenGL clip region management.
Further refine OpenGL wheel zoom user interface
Improve ownship rendering for OpenGL
Repaired the AIS_DEBUG message
Merge pull request #132 from puggan/ais

Repaired the AIS_DEBUG message
Correct AIS CPA alarm acknowledge behavior when not using ACK timeouts.
Correct for very high CPU load factor on OpenGL systems.
Correct for loss of keyboard focus after toolbar zoom.
Improve AIS target list sorting logic for large target counts. (FS#1176)
Merge remote-tracking branch 'upstream/master' into mingw