Fix test/CodeGenCXX/captured-statements.cpp on powerpc64

Generalize some attributes that differ on powerpc64 (i32 vs signext i32). Also
fix some copy-and-pasted code that didn't get updated properly.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181707 91177308-0d34-0410-b5e6-96231b3b80d8