offset enabled for LinePatternSymbolizer
LinePatternSymbolizer visual test
add LinePatternSymbolizer offset python binding
Merge pull request #1991 from PetrDlouhy/master

Offset enabled for LinePatternSymbolizer + tests
MinGW support for SConstruct script. Build now properly detects MinGW and finds dependencies correctly.
Properly Initialize mingwbuild variable.
Added singleton unit test to check for multiple instances across multiple dynamic libraries.
Updates for supporting 64bit MinGW build on Windows 7+ via GNU tools.
Final MinGW 64 bit enhancements for Windows 7+ and Server 2008+