Oscap source

This is not a bug fix. It is needed only after switch to oscap_source. See commit message at 4c0012cbf2e9eac4579fc700ab80f158555ea2f3.

The reason is that `oscap info` haven't previously created oscap_debug.log.*. Now it does.

Previously our code base used couple of different ways to determine SCAP document type. I merged them together and I kept all the features from different implementations that seemed useful. One is that, when OpenSCAP recognize a file type, it will note this fact to the debug log.