- remaked error reporting system.
    libcomps.Comps.fromxml_f and libcomps.Comps.fromxml_str now return
    -1, 0 or 1. 0 means parse procedure completed without any problem,
    1 means there's some errors or warnings but not fatal. -1 indicates
    fatal error problem (some results maybe given, but probably incomplete
    and invalid)
- errors catched during parsing can be obtained by calling
    libcomps.Comps.get_last_parse_errors
- all log is given by
    libcomps.Comps.get_last_parse_log