Auto-sync with upstream branch master
    
    Upstream commit: 1bced8cadc82077f0201801239e89eb24b68e9aa
    
    - Don't put non-ASCII into installed headers
    - Fix spellings of contributor names in comments and doc
    - [MIPS] Raise highest supported EI_ABIVERSION value [SWBZ #24916]
    - mips: Force RWX stack for hard-float builds that can run on pre-4.8 kernels
    - linux: Make profil_counter a compat_symbol (SWBZ#17726)
    - Refactor sigcontextinfo.h
    - Add RTLD_SINGLE_THREAD_P on generic single-thread.h
    - Chinese locales: Set first_weekday to 2 (swbug 24682).
    - powerpc: Fix typos and field name in comments
    - Mark IDN tests unsupported with libidn2 before 2.0.5.
    - Document strftime %Ob and %OB as C2X features.
    - Remove dead regex code
    - Fix bad pointer / leak in regex code
    - Don't use the argument to time.
    - Add tgmath.h macros for narrowing functions.
    - Update i386 libm-test-ulps