Request for reviews (S): 6741738: TypePtr::add_offset() set incorrect offset when the add overflows

[Vladimir Kozlov]

http://webrev.invokedynamic.info/kvn/6741738/index.html

Fixed 6741738: TypePtr::add_offset() set incorrect offset when the add overflows

Problem:
AddPNode::bottom_type() and AddPNode::Value() have the point fix
to prevent an offset add overflows and AddPNode::mach_bottom_type()
does not have it. This leads to the type mismatch in Matcher.

Solution:
TypePtr::add_offset() should set the offset to OffsetBot
when the add overflows.

Reviewed by:
Fix verified (y/n): y, failed test.

Other testing:
JPRT