configure.ac: bump version to 1.9.0-pre

The autoconf version on master is not really important, but this is
what we typically do on master once a release (or release candidate)
has been created for the previous series. I suppose it could be useful
in the context of a non-release tarball (i.e. when there is no git repo
present to tell you the actual hash) but that seems like a very limited
use scenario.

Author: jwpeterson

Diff for: configure.ac

@@ -2,7 +2,7 @@
 # configure.ac file for libmesh.  Used by Automake to generate
 # aclocal.m4 and Makefile.in. See also: http://tinyurl.com/hatuyfn
 # --------------------------------------------------------------
-AC_INIT([libmesh],[1.8.0-pre],[https://github.com/libMesh/libmesh/discussions],[libmesh],[http://libmesh.github.io])
+AC_INIT([libmesh],[1.9.0-pre],[https://github.com/libMesh/libmesh/discussions],[libmesh],[http://libmesh.github.io])
 AC_PREREQ([2.68])
 
 # by default CFLAGS and CXXFLAGS are set to '-g -O2' on systems that support them.