Auto-sync with upstream branch master
    
    Upstream commit: e52434a2e4d1105272daaef87678da950fbec73f
    
    - benchtests: Restore the clock_gettime option
    - Update HP_TIMING_NOW for _ISOMAC in sysdeps/generic/hp-timing.h
    - Replace val with __val in TUNABLE_SET_VAL_IF_VALID_RANGE
    - support: Fix detecting hole support on >2KB-block filesystems
    - powerpc: Fix powerpc64le due a7a3435c9a
    - manual/jobs.texi: remove unused var from example code
    - powerpc/fpu: use generic fma functions
    - aarch/fpu: use generic builtins based math functions
    - ieee754: provide gcc builtins based generic fma functions
    - ieee754: provide gcc builtins based generic sqrt functions
    - Linux: Use __pthread_attr_setsigmask_internal for timer helper thread
    - nptl: Add pthread_attr_setsigmask_np, pthread_attr_getsigmask_np
    - nptl: Make pthread_attr_t dynamically extensible
    - nptl: Destroy the default thread attribute as part of freeres
    - nptl: Change type of __default_pthread_attr
    - nptl: Use __pthread_attr_setaffinity_np in pthread_getattr_np
    - nptl: Use __pthread_getattr_default_np in pthread_create
    - nptl: Add internal alias __pthread_getattr_default_np
    - htl: Fix gsync_wait symbol exposition
    - htl: Make pthread_cond_destroy wait for threads to be woken
    - htl: Enable more cond tests
    - tst-cond11: Fix build with _SC_MONOTONIC_CLOCK > 0
    - mbstowcs: Document, test, and fix null pointer dst semantics (Bug 25219)
    - build: Use FAIL_EXIT1 () on failure to exec child [BZ #23990]
    - manual: Fix backtraces code example [BZ #10441]
    - hurd: Fix fexecve
    - i386: Remove unused file sysdeps/unix/i386/sysdep.S
    - hurd: fix ptsname error when called on a non-tty
    - hurd: Fix fdopendir checking for directory type
    - i386: Remove NO_TLS_DIRECT_SEG_REFS handling
    - Hurd: Move <hurd/sigpreempt.h> internals into wrapper header
    - Hurd: Use __sigmask in favor of deprecated sigmask
    - hurd: Fix pselect atomicity
    - elf: Remove extra hwcap mechanism from ldconfig
    - elf: Do not read hwcaps from the vDSO in ld.so
    - linux: Use internal DIR locks when accessing filepos on telldir
    - Update i386 libm-test-ulps
    - htl: Add clock variants
    - signal: Deprecate additional legacy signal handling functions
    - elf: Turn _dl_printf, _dl_error_printf, _dl_fatal_printf into functions
    - x86: Update Intel Atom processor family optimization
    - elf.h: add aarch64 property definitions
    - elf.h: Add PT_GNU_PROPERTY
    - <libc-symbols.h>: Add libpthread hidden alias support
    - nptl: Use __pthread_attr_copy in pthread_setattr_default_np
    - nptl: Use __pthread_attr_copy in pthread_getattr_default_np (bug 25999)
    - nptl: Add __pthread_attr_copy for copying pthread_attr_t objects
    - nptl: Make __pthread_attr_init, __pthread_attr_destroy available internally
    - nptl: Move pthread_gettattr_np into libc
    - nptl: Move pthread_getaffinity_np into libc
    - nptl: Move pthread_attr_setaffinity_np into libc
    - nptl: Replace some stubs with the Linux implementation
    - Linux: Add missing handling of tai field to __ntp_gettime64
    - Mention GCC 10 attribute access.
    - y2038: Replace __clock_gettime with __clock_gettime64
    - manual: Add missing section and node for clockid_t wait functions
    - y2038: linux: Provide __ntp_gettimex64 implementation
    - y2038: linux: Provide __ntp_gettime64 implementation
    - y2038: Provide conversion helpers for struct __ntptimeval64
    - y2038: Introduce struct __ntptimeval64 - new internal glibc type
    - y2038: linux: Provide __adjtime64 implementation
    - y2038: linux: Provide ___adjtimex64 implementation
    - y2038: linux: Provide __clock_adjtime64 implementation
    - ldconfig: Default to the new format for ld.so.cache
    - nss_compat: internal_end*ent may clobber errno, hiding ERANGE [BZ #25976]
    - powerpc: Optimized rawmemchr for POWER9
    - x86: Add --enable-cet=permissive
    - Remove NO_CTORS_DTORS_SECTIONS macro
    - elf: Assert that objects are relocated before their constructors run
    - powerpc: Optimized stpcpy for POWER9
    - powerpc: Optimized strcpy for POWER9
    - x86: Move CET control to _dl_x86_feature_control [BZ #25887]
    - sunrpc/tst-udp-*: Fix timeout value
    - Linux: Remove remnants of the getcpu cache
    - Update timezone code from tzcode 2020a
    - aarch64: fix strcpy and strnlen for big-endian [BZ #25824]
    - locale: Add transliteration for Geresh, Gershayim (U+05F3, U+05F4)
    - string: Fix string/tst-memmove-overflow to compile with GCC 7
    - Add arch-syscall.h dependency for generating sysd-syscalls file
    - arm: XFAIL string/tst-memmove-overflow due to bug 25620
    - elf: Remove redundant add_to_global_resize_failure  call from dl_open_args
    - string: Add string/tst-memmove-overflow, a test case for bug 25620
    - support: Add support_blob_repeat_allocate_shared
    - nptl: wait for pending setxid request also in detached thread (bug 25942)
    - aarch64: Accept PLT calls to __getauxval within libc.so
    - Use unsigned constants for ICMP6 filters [BZ #22489]
    - Linux: Enhance glibcsyscalls.py to support listing system calls