Remove hard-coded memory settings for 64bit Java 6

maxmem is no longer set for javac and javadoc in
etc/local.properties.example. Nor are these set by
build.py. If the system is detected to be a 64 bit
Java 6 VM, then no properties are set at all.

Otherwise, defaults are taken.

Note: my local environment had javac.maxmem set in
ANT_OPTS which has likely made this more complicated
then it ever needed to be.
Include amd64 in special handling
Support 1.6 and above via ant trick
Merge pull request #990 from joshmoore/javac-mem

Remove hard-coded memory settings for 64bit Java 6