[InstCombine] Add test cases demonstrating failure to handle (select (icmp eq...

[InstCombine] Add test cases demonstrating failure to handle (select (icmp eq (and X, C1), 0), Y, (or Y, C2)) when the icmp portion gets turned into a truncate and a signed compare with 0.

InstCombine has an optimization that recognizes an and with the sign bit of legal type size and turns it into a truncate and compare that checks the sign bit. But the select handling code doesn't recognize this idiom.

llvm-svn: 305338