if_python build on mingw32/mingw64(msys2)

[mattn]

Currently, we can't build if_python on windows with python2 or python3 that is provided from mingw32/mingw64 on msys2.
Most of users download python from https://www.python.org/. And link to library made by msvc.

Below is a patch to enable link to library provided from mingw32/mingw64 on msys2.

https://gist.githubusercontent.com/mattn/4f17789cdc0ec1ad17e9/raw/149ab7e82e6801fcd916956acc8a873b924fa192/gistfile1.diff

You can build vim.exe/gvim.exe with if_python like below.

mingw32-make -f Make_ming.mak GUI=no IME=yes MBYTE=yes ICONV=yes DEBUG=no PYTHON=c:/msys64/mingw64 PYTHON_HOME=c:/msys64/mingw64 PYTHONINC=-Ic:/msys64/mingw64/include/python2.7 DYNAMIC_PYTHON=yes PYTHON_VER=27 DYNAMIC_PYTHON_DLL=libpython2.7.dll ARCH=x86-64 STATIC_STDCPLUS=yes %*

For example, cpsm (https://github.com/nixprime/cpsm) doesn't work with conbination of mingw-gcc and python2 that is downloaded from python official site. But this fix the problem.

- mattn

[Bram Moolenaar]

Thanks. Perhaps that example can be added to one of the INSTALL files?

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[mattn]

okay, updated.

https://gist.githubusercontent.com/mattn/4f17789cdc0ec1ad17e9/raw/20391843cdb1beb784fcb9c235bb35d9d6967474/gistfile1.diff