Subzero: Use llvm::ilist<> for PhiList and AssignList.

Subzero: Use llvm::ilist<> for PhiList and AssignList.

This is toward the goal of pulling non-POD fields out of the CfgNode
class so that CfgNode can be arena-allocated and not leak memory.

For now, PhiList and AssignList are defined as InstList.  Ideally,
they would be ilist<> of InstPhi and InstAssign, but SFINAE happens.

BUG= none
R=jvoung@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=1502e59a21e77f4f2a32cdef42201291e52899bc

[Jim Stichnoth, 2014-12-11 00:46:50]

stichnot@chromium.org changed reviewers:
+ jvoung@chromium.org

[jvoung (off chromium), 2014-12-11 17:00:33]

lgtm

[Jim Stichnoth, 2014-12-11 17:22:57]

Committed patchset #1 (id:1) manually as
1502e59a21e77f4f2a32cdef42201291e52899bc (presubmit successful).