Fix PR6503. This turned into a much more interesting and nasty bug. Various

parts of the cmp|cmp and cmp&cmp folding logic wasn't prepared for vectors
(unrelated to the bug but noticed while in the code) and the code was 
*definitely* not safe to use by the (cast icmp)|(cast icmp) handling logic
that I added in r95855.  Fix all this up by changing the various routines
to more consistently use IRBuilder and not pass in the I which had the wrong 
type.

llvm-svn: 97801