Update ImageMagick to 6.9.0-10.

• USES=pkgconfig:both since the *-config scripts are wrappers around pkg-config.
• Don't require ghostscript for the freetype2 option.
• Actualy remove the pkg-help file with is obsolete since r377347 when the library names where normalized.

Due to libMagick++-6.so bump, chase depend ports.