ptsname_r: Work around bug on Android 4.3. * m4/ptsname_r.m4 (gl_FUNC_PTSNAME_R): Define HAVE_ESSENTIALLY_WORKING_PTSNAME_R. Test whether the return value is correct. * lib/ptsname_r.c (__ptsname_r): If HAVE_ESSENTIALLY_WORKING_PTSNAME_R is defined, just fix the return value. * doc/glibc-functions/ptsname_r.texi: Mention the Android bug. Reword: The behaviour of musl libc is nothing to be "fixed", since it is compliant with the next POSIX standard.

Files:
tests/test-memchr.c
tests/zerosize-ptr.h
tests/signature.h
tests/macros.h
m4/mmap-anon.m4

Depends-on:
extensions
getpagesize

configure.ac:
dnl Check for prerequisites for memory fence checks.
gl_FUNC_MMAP_ANON
AC_CHECK_HEADERS_ONCE([sys/mman.h])
AC_CHECK_FUNCS_ONCE([mprotect])

Makefile.am:
TESTS += test-memchr
check_PROGRAMS += test-memchr