+ * Does not modify the input command line.
+ *
+ * The final parameter (argstart) is used to return a second array
+ * of char * pointers, the same length as argv, each one pointing
+ * at the start of the corresponding element of argv in the
+ * original command line. So if you get half way through processing
+ * your command line in argc/argv form and then decide you want to
+ * treat the rest as a raw string, you can. If you don't want to,
+ * `argstart' can be safely left NULL.