glibc: security bump to the latest 2.26 branch

glibc: security bump to the latest 2.26 branch

List of fixes from the 2.26 branch NEWS files:

  CVE-2017-15670: The glob function, when invoked with GLOB_TILDE,
  suffered from a one-byte overflow during ~ operator processing (either
  on the stack or the heap, depending on the length of the user name).
  Reported by Tim Rühsen.

  CVE-2017-15671: The glob function, when invoked with GLOB_TILDE,
  would sometimes fail to free memory allocated during ~ operator
  processing, leading to a memory leak and, potentially, to a denial
  of service.

  CVE-2017-15804: The glob function, when invoked with GLOB_TILDE and
  without GLOB_NOESCAPE, could write past the end of a buffer while
  unescaping user names.  Reported by Tim Rühsen.

  CVE-2017-17426: The malloc function, when called with an object size near
  the value SIZE_MAX, would return a pointer to a buffer which is too small,
  instead of NULL.  This was a regression introduced with the new malloc
  thread cache in glibc 2.26.  Reported by Iain Buclaw.

Cc: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>