initial import of MPC 1.0.3 package. changes since 1.0.1:

Changes in version 1.0.3:
- Fixed mpc_pow, see
http://lists.gforge.inria.fr/pipermail/mpc-discuss/2014-October/001315.html
- #18257: Switched to libtool 2.4.5.

Changes in version 1.0.2:
- Fixed mpc_atan, mpc_atanh for (+-0, +-1), see
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57994#c7
- Fixed mpc_log10 for purely imaginary argument, see
http://lists.gforge.inria.fr/pipermail/mpc-discuss/2012-September/001208.html