RFR: 8023957: Lock down version of autoconf

[Erik Joelsson]

Following the discussion about the autoconf version, here is a patch 
that changes the AC_PREREQ macro to require at least 2.69. For now, 
since there are no newer versions, this will make us require version 
2.69. I also removed the workaround for getting 2.67 that was put into 
autogen.sh.

http://cr.openjdk.java.net/~erikj/8023957/webrev.root.01/

/Erik