http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50900
--- Comment #11 from karl at freefriends dot org 2011-10-28 23:25:25 UTC --- By "the Texinfo for lgpl 2.1" I mean the Texinfo source document for LGPLv2.1. To be even more specific, what's needed is to replace copying-lib.texi with the contents of http://www.gnu.org/licenses/lgpl-2.1.texi (and making the other adjustments as I wrote about). Then the libiberty document will process with any released texinfo.tex.
