[VFS-483][RAM] Many suggestions to improve the RAM file provider. Use long for FS size limit. Apply test patch https://issues.apache.org/jira/secure/attachment/12596890/unittest-fsoption.patch. Thanks to Bernd Eckenfels.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/vfs@1511900 13f79535-47bb-0310-9956-ffa450edef68