Add libtool patch to handle -Wl,--as-needed

This adds patches for Libtool to fix the handling of -Wl,--as-needed/-Wl,--no-as-needed and -Wl,--whole-archive/-Wl,--no-whole-archive (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=347650).

We are mostly interested in the proper handling of -Wl,--as-needed, which we rely on when building ICON. This patch will help get the shared version of a bundled library free from redundant dependencies meant for other bundled libraries.

This also updates contrib/00nagfor-libtool-patch/nagfor-libtool-2.4.2.patch, which I could not apply without fixing the line numbers.