Somehow, this ADT got missed which is moderately terrifying considering
the efficiency of move for it.

The code to implement move semantics for it is pretty horrible
currently but was written to reasonably closely match the rest of the
code. Unittests that cover both copying and moving (at a basic level)
added.

llvm-svn: 195239

This time tested on both OSX and Linux.

llvm-svn: 178377

This reverts commit 617330909f0c26a3f2ab8601a029b9bdca48aa61.

It broke the bots:

/home/clangbuild2/clang-ppc64-2/llvm.src/unittests/ADT/SmallVectorTest.cpp:150: PushPopTest
/home/clangbuild2/clang-ppc64-2/llvm.src/unittests/ADT/SmallVectorTest.cpp:118: Failure
Value of: v[i].getValue()
  Actual: 0
Expected: value
Which is: 2

llvm-svn: 178334

being power-of-two sized.

llvm-svn: 178332

SmallPtrSet: Provide a more efficient implementation of swap than the default triple-copy std::swap.

This currently assumes that both sets have the same SmallSize to keep the implementation simple,
a limitation that can be lifted if someone cares.

llvm-svn: 152143