Refactor construction of polymorphic loads, stores, and calls.

Refactor construction of polymorphic loads, stores, and calls.

Rather than passing in a pair of unequal-length lists, pass the default
subgraph separately.  Construct the typecase from the top down rather than
the bottom up, so it doesn't need an intermediate zone list.

Also, change a basic block's 'last' instruction field to really be its last
instruction by correctly updating it when inserting and removing
instructions.

Committed: http://code.google.com/p/v8/source/detail?r=6783

[Mads Ager (chromium), 2011-02-15 07:47:04]

LGTM