tests: re-enable strict map loading tests
fix #2090
visual tests: re-enable and update malayalam, bengali, and khmer renderings
visual tests: fix rendering of khmer, malayalam, and bengali 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+