Log Message:
Upgrade ImageMagick from version 6.9.0-5 to 6.9.1-1.

Upstream changes (from their change log):
 * New version 6.9.1-1, SVN revision 18308.
 * Skip empty frames when comparing layers (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=27234).
 * New version 6.9.1-0, SVN revision 18245.
 * Grayscale DPX image files are no longer skewed (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=27209).
 * Fix integer overflow when scaling a 1-bit sample to Q64 (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=27195).
 * New version 6.9.0-10, SVN revision 18299.
 * Account for differences in image size when comparing two images
   (bug report from Dirk).
 * Set an upper ceiling compression with -quality and jpeg:extent (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=2&t=27071).
 * New version 6.9.0-9, SVN revision 18179.
 * Writing histograms / mpeg working again (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=27089).
 * The -linear-stretch option worked for Q16 but not Q32 (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=27112).
 * 6.9.0-8 Bogus release, withdrawn.
 * New version 6.9.0-7, SVN revision 18067.
 * Line strokes appeared too thin (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=26927).
 * Keep text in caption area (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=22504).
 * New version 6.9.0-6, SVN revision 18010.
 * Fixed command line execution in Windows for delegates that move files
   (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=27027).
 * A transient bug for the write MSL element (reference
   http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=27022).
 * Remove uninitialized, unused "p++" from coders/png.c, MNG reader.
 * Initialize "length" in coders/png.c, WriteJNGImage().
 * Fix signed/unsigned mismatch in coders/png.c, MNG reader.