setup.py: added support for building on windows.
setup.py: added support for building on windows.

build():
    Don't specify '-b 0' on Windows, because there is no mupdf.dll.

    Use platform.system() instead of os.uname() (the latter is unix-only).

    Improved code that figures out whether to use clang-python and/or swig.

    Put cpu and python ids into build directories; helps avoid unnecessary
    rebuilding when building multiple wheels.

sdist():
    Added new pickle files and platform/c++/windows_mupdf.def.

clean():
    Specify <root_dir> to pipcl and return paths to delete. This is safer than
    trying to delete files ourselves - pipcl now does some checks.

General:
    Use functions instead of global variables, for clarity.

    Made package description much more detailed because it appears on pypi's
    main mupdf page.

    Improved handling of minimal build.

    When running scripts/mupdfwrap.py, run with sys.executable so we don't have
    to find python.

    On Windows, specify --swig-windows-auto when running mupdfwrap.py so that
    we automatically download and install swigwin as required.

    Use quotes in some commands in case paths have spaces.

ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,ccxvii/mupdf,ccxvii/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,ccxvii/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,ccxvii/mupdf,ccxvii/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,ccxvii/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf