Attempt to have a working build for Python 3.7 under windows with appveyor.

- Python 3.7 is built using Visual Studio 2017 so we use the corresponding image.
- Python 3.7 replaces Python 2.7 when building the module.
- Adding the library legacy_stdio_definitions to the linker input as starting with VS 2015 some symbols have been inlined but may be expected by older binaries. This compatibility library exposes these symbols so they can be dynamically linked when required (Cf. https://stackoverflow.com/a/32418900).

appveyor.yml

@@ -1,5 +1,7 @@
 version: '2.1.{build}'
 
+image: Visual Studio 2017
+
 install:
   - set PATH=%PATH%;C:\msys64\mingw32\bin
 
@@ -7,7 +9,7 @@ build_script:
   - cd miniupnpc
   - appveyor AddCompilationMessage "Building miniupnpc"
   - mingw32-make -f Makefile.mingw
-  - mingw32-make -f Makefile.mingw pythonmodule PYTHON=C:\Python27\python
+  - mingw32-make -f Makefile.mingw pythonmodule PYTHON=C:\Python37\python
 #  - upnpc-static.exe -l
 
 after_build:

miniupnpc/Makefile.mingw

@@ -46,7 +46,7 @@ libminiupnpc.a:	$(OBJS)
 	$(AR) cr $@ $?
 
 pythonmodule:	libminiupnpc.a
-	$(PYTHON) setupmingw32.py build --compiler=mingw32
+	$(PYTHON) setupmingw32.py build
 	$(PYTHON) setupmingw32.py install --skip-build
 
 miniupnpc.dll:	libminiupnpc.a $(OBJSDLL)

miniupnpc/setupmingw32.py

@@ -22,7 +22,7 @@ setup(name="miniupnpc",
       description='miniUPnP client',
       ext_modules=[
          Extension(name="miniupnpc", sources=["miniupnpcmodule.c"],
-                   libraries=["ws2_32", "iphlpapi"],
+                   libraries=["ws2_32", "iphlpapi", "legacy_stdio_definitions"],
                    extra_objects=["libminiupnpc.a"])
       ])