Implement int bit-wise not operation in the optimizing compiler.

- Add support for the not-int (integer one's complement
  negate) instruction in the optimizing compiler.
- Extend the HNot control-flow graph node type and make it
  inherit from HUnaryOperation.
- Generate ARM, x86 and x86-64 code for integer HNeg nodes.
- Exercise these additions in the codegen_test gtest, as there
  is not direct way to assess the support of not-int from a
  Java source.  Indeed, compiling a Java expression such as
  `~a' using javac and then dx generates an xor-int/lit8 Dex
  instruction instead of the expected not-int Dex instruction.
  This is probably because the Java bytecode has an `ixor'
  instruction, but there's not instruction directly
  corresponding to a bit-wise not operation.

Change-Id: I223aed75c4dac5785e04d99da0d22e8d699aee2b