Update warning filtering for after JVM version changes from 1.5 to 1.6

With patch for CLJ-1268 to change default JVM version from 1.5 to 1.6,
the warning message produced when compiling with JDK 1.7 and higher
changes.  Modify my regex that allows this particular warning so it
allows either 1.5 or 1.6, so it works before and after CLJ-1268 is
applied.