[analyzer] IdenticalExpr: use getBytes rather than getString to compare string literals.

PR20693. Patch by Anders Rönnholm.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@216075 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] IdenticalExpr: don't try to compare integer literals with different widths.

PR20659. Patch by Anders Rönnholm.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@216076 91177308-0d34-0410-b5e6-96231b3b80d8