MgCoordinateSystemMgrs::ConvertFromLonLat gives wrong result in release mode

[hugueswski]

The call to the CsMap API CScalcMgrsFromLl uses strlen on the input string instead of sizeof In debug builds the default content of the string "szMgrs" is not the same as the one in release mode and provides unpredictable output strings that can range from no output to the expected output. The computed value was correct but the string result is truncated

[waltweltonlair]

This was fixed with r4324.