Add directory for C++ tests.
Change in preparation for moving all existing tests into cxx/,
and ultimately adding C-specific tests.

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@522 812d1f90-f944-d88a-411a-122bdc93e1ea
Move all tests to tests/cxx.
This commit is risky, so I'm expecting I'll have to revert it.
Details:
- svn mv tests/* tests/cxx/
- dos2unix tests/cxx/* (because svn mv on Windows changes line endings :-()
- Update all references to tests/ in test files to tests/cxx/, both #includes and IWYU assertions
- Update references in run_iwyu_tests.py from tests/ to tests/cxx/
- Fix reference to test/ in comment_pragmas-d3.h, should have been tests/ and now tests/cxx

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@523 812d1f90-f944-d88a-411a-122bdc93e1ea
Clean up line endings after r523

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@524 812d1f90-f944-d88a-411a-122bdc93e1ea
Add directory for C tests.

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@525 812d1f90-f944-d88a-411a-122bdc93e1ea