use VC++ generated DLL files in msys

1. make your DLL file with export symbols project by VC++, you should have AAA.dll and AAA.lib
2. to generate libAAA.a for msys or cygwin to use, you should:
   1. generate AAA.def by pexports.exe in msys
      % pexports.exe AAA.dll > AAA.def
   2. generate libAAA.a by dlltool.exe in msys
      % dlltool.exe -D AAA.dll -d AAA.def -l libAAA.a
3. remember to re-define AAAAPI_EXPORTS as blank which is generated by VC++ in AAA.h as you create the export symbol project.
   #define AAAAPI_EXPORTS __declspec(dllimiport)
--> #define AAAAPI_EXPORTS
   or you will get the link error:
   error LNK2001: unresolved external symbol __imp__FUNC