CBD-774: Add support for automake 1.13

Change-Id: Iba59eec8dcd0d0581f514b9e83a897e5deeb7c61
Reviewed-on: http://review.couchbase.org/23974
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>

configure.ac

@@ -7,7 +7,7 @@ AC_CONFIG_AUX_DIR(config)
 AC_CANONICAL_SYSTEM
 AC_CONFIG_SRCDIR(Makefile.am)
 AM_INIT_AUTOMAKE(subdir-objects foreign)
-AM_CONFIG_HEADER(config.h)
+AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_MACRO_DIR([m4])
 
 AC_PROG_CC