[docs] Teach CMake docs build how to generate Qt Creator help/documentation files.

Patch by Konrad Kleine.

Differential Revision: http://llvm-reviews.chandlerc.com/D2967

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203272 91177308-0d34-0410-b5e6-96231b3b80d8
[ADT] Update PointerIntPair to handle pointer types with more than 31 bits free.

Previously, the assertions in PointerIntPair would try to calculate the value
(1 << NumLowBitsAvailable); the inferred type here is 'int', so if there were
more than 31 bits available we'd get a shift overflow.

Also, add a rudimentary unit test file for PointerIntPair.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203273 91177308-0d34-0410-b5e6-96231b3b80d8