Mimic Javac invalid flag handling

[Jesper Öqvist]

Print an invalid flag error message when a non-flag, non-filename is encountered on the command-line. This should mimic the Javac behavior.

Currently JastAddJ assumes the unrecognized flag is a filename and prints a warning that the file does not exist, then JastAddJ crashes because it tried to open the file and failed.

[Jesper Öqvist]

Print error for non-filename, non-option argument

fixes issue #41 (bitbucket)

→ <<cset 5795e804aac2>>