Bump to 1.3.0 branch (unstable version)

configure.ac

@@ -2,8 +2,8 @@
 # Process this file with autoconf to produce a configure script.
 
 AC_PREREQ(2.59)
-AC_INIT(libmodbus, 1.2, stephane.raimbault@gmail.com)
-AM_INIT_AUTOMAKE(libmodbus, 1.2.0)
+AC_INIT(libmodbus, 1.3, stephane.raimbault@gmail.com)
+AM_INIT_AUTOMAKE(libmodbus, 1.3.0)
 
 # Checks for programs.
 AC_PROG_CC