* Preliminary MSYS2 + MinGW build scripts and instructions.
* CMakeLists.txt: MinGW tweaks, enforce C++03, suppress warnings for now.
* Fix some GCC warnings.
* Fix unused parameter warnings coming from Ifc*.h.
* Fix warning regarding unreachable code (++jt) on MSVC.
* Add IfcParse_EXPORT for IfcInvalidTokenException
* Fix potentially uninitialized pointer variables.
* Note about OpenCASCADE cyclic dependencies fix.
* GCC warning fix: don't generate 'current_enum' variable that is only set and not used for anything ever
* Work around -Wmaybe-uninitialized warnings about boost::optional constructs. Also prevent passing of negative values for --bounds.
* Remove unused variable.
* CMakeLists.txt: ENABLE_BUILD_OPTIMIZATIONS for GCC (simply enforce -03)
Dirk Olbrich