glibc: security bump to latest 2.27 branch

glibc: security bump to latest 2.27 branch

Fixed issues are listed in the 2.27 branch NEWS file:

  CVE-2017-18269: An SSE2-based memmove implementation for the i386
  architecture could corrupt memory.  Reported by Max Horn.

  CVE-2018-11236: Very long pathname arguments to realpath function could
  result in an integer overflow and buffer overflow.  Reported by Alexey
  Izbyshev.

  CVE-2018-11237: The mempcpy implementation for the Intel Xeon Phi
  architecture could write beyond the target buffer, resulting in a buffer
  overflow.  Reported by Andreas Schwab.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>