[PATCH] Extend SLPVectorizer for cases where insertelement instructions must be rescheduled

[Arch D. Robison]

  For one of the long lines, I replaced a && with nested if, around line 587 of the revised file.  Since that's beyond mere fixing of whitespace, it would be good if someone gave the patch a final review.

http://llvm-reviews.chandlerc.com/D3143