0.9.11.31: misc win32 improvements

  * Check for correct "expand" in canonicalize-whitespace, and skip
     canonicalization if it doesn't seem right. (Windows "expand" is
     something quite different.)
  * RUN-PROGRAM now always returns a process structure, which reports
     the exit-code of the process when :WAIT was true. :WAIT nil
     process-structures still keep their :RUNNING status indefinitely
     on Windows, though.
  * FIND-EXECUTABLE-IN-SEARCH-PATH actually searches the path, and adds
     "exe" as :TYPE if :TYPE is missing on Windows.
  * ASDF:RUN-SHELL-COMMAND searches for Bourne-shell on Windows, as there
     is no default location.
  * SB-GROVEL directly runs gcc and the groveler instead of indirecting
     via shell, and the groveler directly writes to the lisp-file instead
     of via stdout and shell redirection.
  * Hack SB-POSIX till it builds and passes all applicable tests on Windows.
     Mostly this involved plenty of #-win32, but a few tests needed to
     be adjusted for the delication Microsoft constitution.
  * Implement COPY-STREAM in ASDF-INSTALL so that it doesn't have to
     depend on SB-EXECUTABLE.
  * Take the .exe suffix into account when installing over an old SBCL
     on MSYS.
  * Adjust UNPARSE-NATIVE-WIN32-NAMESTRING slightly: Windows OS functions
     like stat don't like to have directory names ending with a slash.

This is good enough to run unpatched Slime with *COMMUNICATION-STYLE*
NIL, and build & pass tests with all contribs except SB-SIMPLE-STREAMS.