Core 5.1.1

This is a feature and security update to the Core 5 series.

Updates:

• Updated GNU C Library with the newest changes on the 2.26 branch.
• Updated Linux API Headers to 4.14.12.
• Updated Ncurses to 6.0+20171230 to include security and bug fixes.
• Updated Binutils with the newest changes on the 2.29.1 branch.
• Updated MPFR to 4.0.0 (ABI version 6).
• Updated GDBM to 1.14.1.
• Introduced Retpoline patches from Clear Linux for GCC 7.2, to mitigate a
  variant of the Spectre vulnerability.

Changes and Fixes:

• Disabled binary stripping in GNU C Library to aid with debugging.
• Rebuilt GMP to adapt to ABI changes in LibLTO.

What to Expect:

• A smooth update with little incompatibility, though it could happen.