libXpm version packaged with Windows binaries

[Christoph Scholtes <cschol2112@googlemail.com>]

From README.W32:

* Image support

  Emacs has built in support for XBM and PPM/PGM/PBM images, and the
  libXpm library is bundled, providing XPM support (required for color
  toolbar icons and splash screen).  Source for libXpm should be available
  on the same place as you got this binary distribution from.  The version
  of libXpm bundled with this version of Emacs is 3.5.7, based on x.org's
  libXpm library from X11R7.3.


This is obviously not correct since we are packaging libXpm 3.5.8 with
the current Windows binary releases. The sources for 3.5.8 are provided
in the directory where the Windows binaries reside. 

I wanted to update the README.W32 file and was wondering where the 3.5.8
version came from and why there was a need to update from 3.5.7.

Thanks,
Christoph