Bug#557879: graphicsmagick: please build with --with-quantum-depth=16

[debianbug . jthomson]

Please fix this. It's causing a bug in octave too.
— graphicsmagick-1.3.12/debian/rules 2010-08-22 00:36:45.000000000 +0000
+++ debian/rules 2010-08-22 00:42:03.000000000 +0000
@@ -64,6 +64,7 @@CFLAGS=”$(CFLAGS)” CXXFLAGS=”$(CFLAGS)” LDFLAGS=”$(LDFLAGS)” \
./configure $(gm_confflags) \
+ –with-quantum-depth=16 \
–enable-shared \
–enable-static \
–enable-libtool-verbose \