GetExternalDefinitions fix

was missing kw_wchar_t in IsBuiltIn, ln variable unused.
adding test_007.cc

Uses new catalog entries, see index.plex

There is reference dump yet so the test there will fail.
skip loading if no xrefs found

speeds up if there is nothing to do.
Recurse on catalog entries (part 4)

This completes basic recursing
- includes are colapsed
- depth first recursion for example iplx\io_exception -->plx\exception
- catalog\index now contains more entries
adding reference for test_007.cc