Request for reviews (S): 6980978: assert(mt == t->xmeet(this)) failed: meet not commutative

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6980978/webrev

Fixed 6980978: assert(mt == t->xmeet(this)) failed: meet not commutative

TypeAryPtr klass exactness is not symmetric when
one of the poiter is constant array.
And not NULL klass set for bottom[] at the same case.

Solution:
Fix code in TypeAryPtr::xmeet() for constant array.

Tested with failed java regression tests.