* cygpath.cc: Include argz.h.
(options_from_file_flag): Move from main to global static variable.
(mode_flag): Ditto.
(do_sysfolders): Rename from dowin and accommodate throughout.
Don't exit from here.
(do_pathconv): Rename from doit and accommodate throughout.
(print_version): Change copyright.
(do_options): New function, centralizing option processing.
Rework checking options for correctness.
(action): New function, centralizing calling worker functions.
(main): Simplify. Move option processing to do_options. Move calling
worker functions to action. Rework getting arguments from files.