Debug mode: learning to crawl.  I need to set up some tests that actually test that the debug mode is working, but that won't cause problems when debug mode isn't on.  This is my first prototype of such a test.  It should call std::terminate() because it's comparing iterators from different containers.  And std::terminate() is rigged up to exit normally.  If debug mode fails, and doesn't call terminate, then the program asserts.  The test is a no-op if _LIBCPP_DEBUG2 is not defined or is defined to be 0.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@177892 91177308-0d34-0410-b5e6-96231b3b80d8
More vector::iterator debug mode tests.  Run by adding to OPTIONS -D_LIBCPP_DEBUG2=1.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@177897 91177308-0d34-0410-b5e6-96231b3b80d8
Debug mode tests for vector::front and back.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@177904 91177308-0d34-0410-b5e6-96231b3b80d8
Remove some erroneous code I was using to debug debug mode.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@177908 91177308-0d34-0410-b5e6-96231b3b80d8
Added debug tests for indexing, pop_back and both forms of erase.  Added an improved error message for erasing a single element with end().

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@177929 91177308-0d34-0410-b5e6-96231b3b80d8