Adaptation for MSYS2

[eonj]

MSYS2 is a POSIX-complaint environment for Windows. It provides PE binaries built from MinGW-w64 compilers, through pacman which MSYS2 team successfully ported.

I installed mingw-w64-i686-python3, mingw-w64-i686-pip3, mingw-w64-imagemagick using MSYS2 pacman, then run pip3 install wand. It was successful but import wand.image did not work. It was because ImageMagick binaries were installed as /mingw32/bin/libMagick(Core|Wand)-6.Q16HDRI-2.dll (with no $MAGICK_HOME) in my case. As current Wand searches for CORE_RL_(wand|magick)_<suffix>(.dll) on Windows and libMagickWand<suffix>(.so) for almost others, Wand couldn't find the binaries in my case.

This PR includes two commit of changeset over wand/api.py. The former one changes the structure of ImageMagick library probing procedure. find_library(), now renamed library_paths(), became a generator function that iterates for possible library paths. Then load_library() checks if each path is loadable, via ctypes.CDLL(). The latter one, finally appends more example for library path that succeeds in case of MSYS2.

Manually tested in:

• Windows 7 Professional K SP1, x86, MSYS2(MINGW32 shell), Python 3.4
• Ubuntu 14.04.2 kernel 3.13.0-48-generic, x86_64, Python2.7

Thanks to @dahlia who provided proper feedback for me to write these changes.

[dahlia]

Thanks for your effort. 👍