fix for a subtle bug in how HTS engine parses command line arguments

Engine::load() is directly derived from the main() of HTS_engine,
however the main expects that argv[0] is the runnning program name
whereas the config files don't contain that line: argv[0] is usually
the first parameter (e.g. '-s'). This first parameter would get ignored
by the parsing and side-effect such as inappropriate sampling rate would
occur.