BUG-1800: restore QNameModule sharing in parser

The refactor to eliminate use of QName.getPrefix() has lead to us not
sharing QNameModules anymore. Restore the capability to allow us to
operate at pea efficiency.

Change-Id: I9a23ca3396390eae0ffe9d954fb6fab3c7d1be55
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-1800: restore QNameModule sharing in parser"