[Bug libfortran/54572] Use libbacktrace library

[fxcoudert at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54572

--- Comment #16 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> ---
Patch proposed: https://gcc.gnu.org/ml/gcc-patches/2015-08/msg00762.html