constant fold ptrtoint(inttoptr) with target data when available. This allows

us to fold the entry block of PR1602 to false instead of:

br i1 icmp eq (i32 and (i32 ptrtoint (void (%struct.S*)* inttoptr (i64
1 to void (%struct.S*)*) to i32), i32 1), i32 0), label %cond_next, label
%cond_true

llvm-svn: 41023