libtool: for 64bit GNU arches, add /lib64 and /usr/lib64 to sys_lib_dlsearch_path.

* m4/libtool.m4 (_LT_SYS_DYNAMIC_LINKER) <linux*, k*bsd*-gnu>
<kopensolaris*-gnu, gnu*>: If $host_cpu contains "64", add /lib64
and /usr/lib64 to sys_lib_dlsearch_path_spec.
Reported by Orion Poplawski, Christian Rössel, Olly Betts et. al.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
libtool: s390x is also a 64bit glibc/ELF platform.

* m4/libtool.m4 (_LT_SYS_DYNAMIC_LIB): Add s390x to glibc/ELF
compatible CPUs that have /lib64 and /usr/lib64 in
sys_lib_dlsearch_path_spec.
Reported by Pavel Raiskup

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
bootstrap: sync with upstream.

* gl/build-aux/extract-trace (func_find_tool): Quote a bare
variable expansion in a test argument.
* bootstrap: Regenerate.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
maint: fix syntax-check failures.

* m4/m4.m4 (AC_PROG_GNU_M4): Reverse some test arguments for
sc_prohibit_test_const_follows_var.
Remove some spurious braces for
sc_useless_braces_in_variable_drefs.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
libtool: support LT_SYS_LIBRARY_PATH for adjusting bad guesses.

Revert 8728e07 and 440fee6.
Some GNU/Linux distributions install libraries into /lib64 (or
/usr/lib64) on 64-bit machines, while /lib (/usr/lib
respectively) stays for multilib variant.  Other distributions
keep /usr/lib for 64-bit variant and reserve other directory for
multilib. Detection of what approach a given system uses is
difficult, however, especially because Glibc's ldconfig does not
report the full and correct list of search paths. Allow the user
to adjust Libtools heuristically determined search paths with
the new LT_SYS_LIBRARY_PATH environment variable at both
compile-time, when libtool is called, and at configure time.
* m4/libtool.m4 (_LT_PREPARE_MUNGE_PATH_LIST): Define a new
function to munge a libtool path list according to a user
supplied colon-delimited path.
(_LT_SYS_DYNAMIC_LINKER): Require _LT_PREPARE_MUNGE_PATH_LIST.
Mark LT_SYS_LIBRARY_PATH as precious to autoconf (to survive
automatic "autoreconf").
Call the new func_munge_path_list function on
sys_lib_dlsearch_path_spec - this propagates results to
generated libtool script.
(_LT_CONFIG): Expand _LT_PREPARE_MUNGE_PATH_LIST into generated
libtool script.
* build-aux/ltmain.in (func_mode_link): Call it to adjust
sys_lib_dlsearch_path according to LT_SYS_LIBRARY_PATH.
* doc/libtool.texi: Document new LT_SYS_LIBRARY_PATH.
* doc/notes.texi: Likewise.
* NEWS: Update.

References: http://thread.gmane.org/gmane.comp.gnu.libtool.general/8339/focus=8345
Signed-off-by: Gary V. Vaughan <gary@gnu.org>