Auto-sync with upstream branch master
    
    Upstream commit: cbce69e70dc4b04fefcc7257e593733b8b03856c
    
    - Multiple locales: Add date_fmt (bug 24054)
    - Update libc.pot for 2.31 release
    - Add libm_alias_finite for _finite symbols
    - Linux: Fix clock_nanosleep time64 check
    - linux: Fix vDSO macros build with time64 interfaces
    - x86: Make x32 use x86 time implementation
    - Remove vDSO support from make-syscall.sh
    - linux: Update x86 vDSO symbols
    - linux: Update mips vDSO symbols
    - linux: Consolidate Linux gettimeofday
    - linux: Consolidate time implementation
    - elf: Enable relro for static build
    - elf: Move vDSO setup to rtld (BZ#24967)
    - linux: Add support for clock_gettime64 vDSO
    - linux: Optimize fallback 32-bit clock_gettime
    - linux: Enable vDSO clock_gettime64 for i386
    - linux: Enable vDSO clock_gettime64 for arm
    - linux: Enable vDSO clock_gettime64 for mips
    - linux: Add support for clock_getres64 vDSO
    - linux: Optimize fallback 32-bit clock_getres
    - htl: Use dso_handle.h
    - htl: Drop common tcbhead_t definition
    - htl: Move pthread_atfork to libc_nonshared.a
    - htl: Add __errno_location and __h_errno_location
    - hurd: Fix message reception for timer_thread