x11vnc: remove old libtool macros from acinclude.m4

These can cause build problems. We only want macros in acinclude.m4 which
aren't available for aclocal to get elsewhere.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
(cherry picked from commit f6db87726d84976275cfe6b74a9e270f6bf6792e)
Signed-off-by: Armin Kuster <akuster808@gmail.com>