glibc: Update to 2.20

* The following bugs are resolved with this release:

  6804, 9894, 12994, 13347, 13651, 14308, 14770, 15119, 15132, 15347, 15514,
  15698, 15804, 15894, 15946, 16002, 16064, 16095, 16194, 16198, 16275,
  16284, 16287, 16315, 16348, 16349, 16354, 16357, 16362, 16447, 16516,
  16532, 16539, 16545, 16561, 16562, 16564, 16574, 16599, 16600, 16609,
  16610, 16611, 16613, 16619, 16623, 16629, 16632, 16634, 16639, 16642,
  16648, 16649, 16670, 16674, 16677, 16680, 16681, 16683, 16689, 16695,
  16701, 16706, 16707, 16712, 16713, 16714, 16724, 16731, 16739, 16740,
  16743, 16754, 16758, 16759, 16760, 16770, 16786, 16789, 16791, 16796,
  16799, 16800, 16815, 16823, 16824, 16831, 16838, 16839, 16849, 16854,
  16876, 16877, 16878, 16882, 16885, 16888, 16890, 16892, 16912, 16915,
  16916, 16917, 16918, 16922, 16927, 16928, 16932, 16943, 16958, 16965,
  16966, 16967, 16977, 16978, 16984, 16990, 16996, 17009, 17022, 17031,
  17042, 17048, 17050, 17058, 17061, 17062, 17069, 17075, 17078, 17079,
  17084, 17086, 17088, 17092, 17097, 17125, 17135, 17137, 17150, 17153,
  17187, 17213, 17259, 17261, 17262, 17263, 17319, 17325, 17354.

* Reverted change of ABI data structures for s390 and s390x:
  On s390 and s390x the size of struct ucontext and jmp_buf was increased in
  2.19. This change is reverted in 2.20. The introduced 2.19 symbol versions
  of getcontext, setjmp, _setjmp, __sigsetjmp, longjmp, _longjmp, siglongjmp
  are preserved pointing straight to the same implementation as the old ones.
  Given that, new callers will simply provide a too-big buffer to these
  functions. Any applications/libraries out there that embed jmp_buf or
  ucontext_t in an ABI-relevant data structure that have already been rebuilt
  against 2.19 headers will have to rebuilt again. This is necessary in any
  case to revert the breakage in their ABI caused by the glibc change.

* Support for file description locks is added to systems running the
  Linux kernel. The standard file locking interfaces are extended to
  operate on file descriptions, not file descriptors, via the use of
  F_OFD_GETLK, F_OFD_SETLK, and F_OFD_SETLKW. File description locks
  are associated with an open file instead of a process.

* Optimized strchr implementation for AArch64.  Contributed by ARM Ltd.

* The minimum Linux kernel version that this version of the GNU C Library
  can be used with is 2.6.32.

* Running the testsuite no longer terminates as soon as a test fails.
  Instead, a file tests.sum (xtests.sum from "make xcheck") is generated,
  with PASS or FAIL lines for individual tests.  A summary of the results is
  printed, including a list of failing lists, and "make check" exits with
  error status if there were any unexpected failures.  "make check
  stop-on-test-failure=y" may be used to keep the old behavior.

* The am33 port, which had not worked for several years, has been removed
  from ports.

* The _BSD_SOURCE and _SVID_SOURCE feature test macros are no longer
  supported; they now act the same as _DEFAULT_SOURCE (but generate a
  warning).  Except for cases where _BSD_SOURCE enabled BSD interfaces that
  conflicted with POSIX (support for which was removed in 2.19), the
  interfaces those macros enabled remain available when compiling with
  _GNU_SOURCE defined, with _DEFAULT_SOURCE defined, or without any feature
  test macros defined.

* Optimized strcmp implementation for ARMv7.  Contributed by ARM Ltd.

* Added support for TX lock elision of pthread mutexes on s390 and s390x.
  This may improve lock scaling of existing programs on TX capable systems.
  The lock elision code is only built with --enable-lock-elision=yes and
  then requires a GCC version supporting the TX builtins.  With lock elision
  default mutexes are elided via __builtin_tbegin, if the cpu supports
  transactions. By default lock elision is not enabled and the elision code
  is not built.

* CVE-2014-4043 The posix_spawn_file_actions_addopen implementation did not
  copy the path argument.  This allowed programs to cause posix_spawn to
  deference a dangling pointer, or use an unexpected pathname argument if
  the string was modified after the posix_spawn_file_actions_addopen
  invocation.

* All supported architectures now use the main glibc sysdeps directory
  instead of some being in a separate "ports" directory (which was
  distributed separately before glibc 2.17).

* The NPTL implementation of POSIX pthreads is no longer an "add-on".
  On configurations that support it (all Linux configurations), it's now
  used regardless of the --enable-add-ons switch to configure.  It is no
  longer possible to build such configurations without pthreads support.

* Locale names, including those obtained from environment variables (LANG
  and the LC_* variables), are more tightly checked for proper syntax.
  setlocale will now fail (with EINVAL) for locale names that are overly
  long, contain slashes without starting with a slash, or contain ".." path
  components. (CVE-2014-0475)  Previously, some valid locale names were
  silently replaced with the "C" locale when running in AT_SECURE mode
  (e.g., in a SUID program).  This is no longer necessary because of the
  additional checks.

* On x86-64, the dynamic linker's lazy-binding support is now compatible
  with application code using Intel MPX instructions.  (With all previous
  versions, the MPX register state could be clobbered when making calls
  into or out of a shared library.)  Note that while the new dynamic
  linker is compatible with all known x86 hardware whether or not it
  supports Intel MPX, some x86 instruction-set emulators might fail to
  handle the new instruction encodings.  This is known to affect Valgrind
  versions up through 3.9 (but will be fixed in the forthcoming 3.10
  release), and might affect other tools that do instruction emulation.

* Support for loadable gconv transliteration modules has been removed.
  The support for transliteration modules has been non-functional for
  over a decade, and the removal is prompted by security defects.  The
  normal gconv conversion modules are still supported.  Transliteration
  with //TRANSLIT is still possible, and the //IGNORE specifier
  continues to be  supported. (CVE-2014-5119)

* Decoding a crafted input sequence in the character sets IBM933, IBM935,
  IBM937, IBM939, IBM1364 could result in an out-of-bounds array read,
  resulting a denial-of-service security vulnerability in applications which
  use functions related to iconv. (CVE-2014-6040)
xz: Update to 5.0.6