RFR(S): 8202950: C2: assert(found_sfpt) failed: no node in loop that's not input to safepoint

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8202950/webrev.00/

A Load outside the outer and inner strip mined loop has a control edge
to the inner loop. When the loop is unrolled, the control is changed to
be right out of the inner loop. That confuses verification code that
expects no node to have a control set to the inner loop exit unless it's
referenced from the safepoint node. Rather than weaken the verification
code, the fix I suggest is that on loop cloning for unrolling, the
control of the Load be set to be outside the outer loop as well.

Roland.