There is the following problem, the library /usr/lib/libdevhelp-1.so does not set the rpath/runpath tags for linking with mozilla or mozilla-firefox. Expected readelf -d /usr/lib/libdevhelp-1.so|grep -E RUNPATH\|RPATH, should show /usr/lib/mozilla or another corresponding path, in which the linked libraries are to be found. This could probably lead to problems by dynamic resolution of the libraries. There is also a bug report about this in gnome-bugzilla http://bugzilla.gnome.org/show_bug.cgi?id=166968. I'll attach a slightly modified version (patching Makefile.in not Makefile.am and removing the other patches) of this patch, which resolves the issue.
Created attachment 64621 [details, diff] devhelp-rpath.patch This will set the rpath/runpath tags for /usr/lib/libdevhelp-1.so to the correct path of mozilla or mozilla-firefox-libraries.
Created attachment 65917 [details] devhelp-0.10-r1.ebuild The ebuild which uses this patch.
This bug is rendered invalid with the new mozilla and mozilla-firefox ebuilds, which use the -Wl,-R linker directive in the pkg-config files.