* aclocal.m4: Include acx.m4 and no-executables.m4.
(libiberty_AC_FUNC_STRNCMP): Use AC_LIBOBJ.
(LIB_AC_PROG_CC): Remove.
* configure.in: Update AC_PREREQ to 2.57. Use GCC_NO_EXECUTABLES.
Use AC_PROG_CC and set ac_libiberty_warn_cflags instead of using
LIB_AC_PROG_CC. Use AC_LIBOBJ. Call AC_ISC_POSIX later, only if
performing link tests.
* configure: Regenerated.