cpp11-migrate: Factor out duplicate code in UseNullPtr

This moves the actual replacement code into a separate
function. There is still a bit of code duplication to
go from macros to expansion areas, but that code will
need to be fixed anyways to resolve bugs around macro
replacement.

Reviewed by: Tareq Siraj, Edwin Vane



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@176372 91177308-0d34-0410-b5e6-96231b3b80d8
Fix recursive make in clang-tools-extra

Autoconf make (all) now properly recurses from tools/extra/Makefile into
tools/extra/test/Makefile and tools/extra/test/cpp11-migrate/Makefile. The
'all' target is responsible for creating lit config files and autogenerating
tests. Subsequent 'check-all' targets will properly work.

Re-enabling UseAuto/iterator.cpp test.

General clean-up of clang-tools-extra makefiles; removing dead targets and
removing duplicated pieces of llvm/Makefile.rules.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@176373 91177308-0d34-0410-b5e6-96231b3b80d8