[PATCH] CodeGenPrep: sink extends of illegal types into use block.

[NAKAMURA Takumi]

  This passes on at least one selfhost builder.
  http://bb.pgr.jp/builders/clang-3stage-i686-linux/builds/99

  It's a bugfix. I think it can be committed.

http://llvm-reviews.chandlerc.com/D3021

BRANCH
  mul128_2

ARCANIST PROJECT
  llvm