PIDL: fix parsing linemarkers in preprocessor output

PIDL: fix parsing linemarkers in preprocessor output

When PIDL calls out to C preprocessor to expand IDL files
and parse the output, it filters out linemarkers and line control
information as described in http://gcc.gnu.org/onlinedocs/cpp/Preprocessor-Output.html
and http://gcc.gnu.org/onlinedocs/cpp/Line-Control.html#Line-Control

With gcc 4.8 stdc-predef.h is included automatically and linemarker for the
file has extended flags that PIDL couldn't parse ('system header that needs to
be extern "C" protected for C++')

Thanks to Jakub Jelinek <jakub@redhat.com> for explanation of the linemarker format.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=906517

Reviewed-by: Andreas Schneider <asn@samba.org>