Handle relative includes, which escapes .inspector-includes/ better

[Mic92]

If I a file is relative to the compiler in an parent directory (ex.: gcc ../../test.cpp) then FILE contains also ...
This makes generated headers ending up outside the hidden directory .inspector-includes.

Possible hacky solution: Put headers in a sub-sub-sub-sub... directory (.inspector-includes/a/a/a/a/a/a) and print a warning if this level get exceeded.