Groff 1.19.2 is out since 2005/09/04. The patches need to be reworked to apply against this version.
Created attachment 73087 [details] groff-1.19.2-infoext.patch
Created attachment 73088 [details] groff-1.19.2-no-netpbm-depend.patch
Created attachment 73089 [details] groff-1.19.2-parallel-make.patch
thanks, now in portage