As I already said in the 'Summary' field, I tried to emerge yelp 2.14.0 but did not succed: it needed GNOME_DEBUG_CHECK and other macros from gnome-common.m4. Then I emerged gnome-common and everything went fine!
These commands are not required for compiling - at least you can comment them out (in configure) and compile the source code without problems. I noticed that configure complained about GNOME_COMMON_INIT as well but didn't stopped there. There seems to be a definition which macros are allowed to fail and which aren't. In this case GNOME_DEBUG_CHECK and GNOME_COMPILE_WARNINGS should be added to this "might fail" list.
it must be depend on gnome-common, otherwise, yelp will fail to build. I have tried from a new installed system. not a upgrade, untill gnome-common-2.12 installed, yelp won't compile.
the gnome-common dep is unnecessary. they included the macros in the m4's, we just needed to make sure they were preserved after running aclocal & friends. in cvs.