Upgrade to libtool 2.4.7.
* m4/libtool.m4: Update from libtool-2.4.7, with modifications.
2017-10-21 Bruno Haible <bruno@clisp.org>
Fix -export-symbols and -export-symbols-regex support on Solaris 11.3.
* m4/libtool.m4 (_LT_CMD_GLOBAL_SYMBOLS): Adjust symcode for Solaris.
* m4/ltoptions.m4: Likewise.
* m4/ltsugar.m4: Likewise.
* m4/ltversion.m4: Likewise.
* m4/lt~obsolete.m4: Likewise.
* build-aux/ltmain.sh: Likewise.
