Remove unnecessary include of sys/mman.h

Only include sys/wait.h on platforms that have it.

Include winsock.h rather than arpa/inet.h on mingw platforms.
Also fix a trivial int/long mismatch.

Don't attempt to use chroot() on systems that don't support it.

This has the added bonus of allowing us to use popen() rather than
fork()/exec() for improved portability. Of course, the loss of an
install root is a major reduction of functionality but it's hard to
see what else we could substitute for chroot().

Don't try and create symbolic links on platforms that don't support symlink()

Support platforms where mkdir only takes one argument (eg., MS-Windows)

Include limits.h in files which used PATH_MAX for portability

Avoid unportable "uint" type

Add support for platforms without fnmatch.

This uses gnulib so you will need to have a copy in order
to run autogen.sh (but not to build from a tarball). Either
arrange for gnulib-tool to be in your path or set the
environment variable GNULIB_TOOL to point to its location.

Support platforms without mmap