Working in Windows 8.1 and compiling with MinGW

Original code
```xml
<flag value='-DHXCPP_API_LEVEL=${removeQuotes:hxcpp_api_level}' if="hxcpp_api_level" />
```
generate
>haxelib run hxcpp Build.xml haxe -DHXCPP_M64="1" -DO3="1" -Dhaxe3="1" -Dhaxe_ver="3.2" **-Dhxcpp_api_level="312"** -Dmingw="1" -Dno_shared_libs="1" -I"src/" -I"...haxe\\haxe\\extraLibs/" -I"" -I"...haxe\\haxe\\std/cpp/_std/" -I"...haxe\\haxe\\std/"

>>g++.exe -Iinclude -c -O3 -DHXCPP_M64 -DHXCPP_VISIT_ALLOCS **-DHXCPP_API_LEVEL=** -DHX_WINDOWS -DHXCPP_M64 -I.../haxe/haxe/lib/hxcpp/git/include -x c++ -frtti ./src/haxe/Log.cpp -oobj/mingw64/6ddce8a4_Log.o
>>...

instead 
```xml
<flag value='-DHXCPP_API_LEVEL=${hxcpp_api_level}' if="hxcpp_api_level" />
```
generate
>haxelib run hxcpp Build.xml haxe -DHXCPP_M64="1" -DO3="1" -Dhaxe3="1" -Dhaxe_ver="3.2" **-Dhxcpp_api_level="312"** -Dmingw="1" -Dno_shared_libs="1" -I"src/" -I"...\\haxe\\haxe\\extraLibs/" -I"" -I"...\\haxe\\haxe\\std/cpp/_std/" -I"...\\haxe\\haxe\\std/"

>>g++.exe -D_CRT_SECURE_NO_DEPRECATE -DHX_UNDEFINE_H -c -O3 -DHXCPP_M64 -DHXCPP_VISIT_ALLOCS **-DHXCPP_API_LEVEL=312** -DHX_WINDOWS -DHXCPP_M64 -IC:/lg/Dropbox/APPs/haxe/haxe/lib/hxcpp/git/include -x c++ -frtti C:/lg/Dropbox/APPs/haxe/haxe/lib/hxcpp/git/src/hx/StdLibs.cpp -oobj/mingw64/55e62088_StdLibs.o
>>...

working code!!!