Implement >>> inline for the JIT backend

The unsigned right shift operations can use a signed int as input, unifying
the handling with the other shift operations. The only difference now is
in the type of the return value.

Change-Id: Ia9b83568951d1c1c77322d07cd734e2c37d34573
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>