DAG: Combine (and (setne X, 0), (setne X, -1)) -> (setuge (add X, 1), 2)

A common idiom is to use zero and all-ones as sentinal values and to
check for both in a single conditional ("x != 0 && x != (unsigned)-1").
That generates code, for i32, like:
  testl %edi, %edi
  setne %al
  cmpl  $-1, %edi
  setne %cl
  andb  %al, %cl

With this transform, we generate the simpler:
  incl  %edi
  cmpl  $1, %edi
  seta  %al

Similar improvements for other integer sizes and on other platforms. In
general, combining the two setcc instructions into one is better.

rdar://14689217

llvm-svn: 188315

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