never test and always default HAVE_MMAP to on
never test and always default HAVE_MMAP to on

This should alleviate vboxfs problems from issue #1008.

romange/gperftools,gperftools/gperftools,gperftools/gperftools,alk/gperftools,gperftools/gperftools,romange/gperftools,alk/gperftools,alk/gperftools,gperftools/gperftools,romange/gperftools,romange/gperftools,alk/gperftools