vsprintf may change its va_list argument so repeatedly calling it with the same va_list arg is undefined behavior.
Fix this by creating a copy of the va_list argument before each vsprintf call.
- Added ordinal logging level: all, debug, info, error. Compiling with DEBUG defined is no longer necessary for debug logging. Be careful when logging debug level because it produces copious output.
- Fixed -enter-debugger options when compiled with SUPERMODEL_DEBUGGER.
- Command line parse errors no longer ignored; Supermodel will now exit.