Auto-sync with upstream branch master
    
    Upstream commit: 904b94c07af84b7e4c98de3bbb822ccffcaf8c40
    
    - socket: Add a test for MSG_CMSG_CLOEXEC
    - hurd: Do not take any flag from the CMSG_DATA
    - hurd: Implement MSG_CMSG_CLOEXEC
    - hurd: Don't pass FD_CLOEXEC in CMSG_DATA
    - hurd: Implement prefer_map_32bit_exec tunable
    - hurd: Don't attempt to deallocate MACH_PORT_DEAD
    - hurd: Only deallocate addrport when it's valid
    - hurd: Implement MAP_32BIT
    - Use O_CLOEXEC in more places (BZ #15722)
    - misc: Convert daemon () to GNU coding style
    - wcsmbs: Add wcsdup() tests. (BZ #30266)
    - string: Add tests for strndup (BZ #30266)
    - string: Add tests for strdup (BZ #30266)
    - string: Allow use of test-string.h for non-ifunc implementations.
    - hurd: Don't migrate reply port into __init1_tcbhead
    - hurd: Make dl-sysdep's open () cope with O_IGNORE_CTTY
    - Created tunable to force small pages on stack allocation.
    - malloc: Add missing shared thread library flags
    - linux: Re-flow and sort multiline Makefile definitions
    - posix: Re-flow and sort multiline Makefile definitions