Update ImageMagick to 6.9.1-6.

• Remove double --without-lcms.
• Speed up the test target by running it with multiple jobs.
• Finaly add back WITHOUT_X11 to the IM-nox11 port, this will select the ghostscript-nox11 port instead of the x11 version. The code in bsd.port.mk doesn't handle the OPTIONS UNSET/EXCLUDE of X11. [1]

PR: 199268 [1]