[PATCH PING] rebased AIX-driven libtool improvement patches

[Michael Haubenwallner]

Hi Pavel,

as requested, here's two sets of rebased improvement patches to simplify
fixing AIX problems (at least), to be subsequently imported into gcc.

The original posts were:
1: http://lists.gnu.org/archive/html/libtool-patches/2015-05/msg00001.html
2: http://lists.gnu.org/archive/html/libtool-patches/2016-03/msg00000.html

The tests across various AIX configure options were run and compared with:
https://github.com/haubi/libtool-testing/tree/master/aix

Thanks a lot!
/haubi/