Unary Not (boolean and bitwise) is no longer a separate LLVM instruction

Unary Not (boolean and bitwise) is no longer a separate LLVM instruction
but is instead implemented with XOR.  Note that the InstrForest opLabels
for Not and BNot remain the same, i.e., the XOR is recognized and
represented as a (boolean or bitwise) Not when building the instruction
trees.  But these tree nodes are now binary, not unary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3343 91177308-0d34-0410-b5e6-96231b3b80d8