* getopt-long.scm (parse-option-spec): Store 'optional as the
value-required? field for options that take optional values.
(process-short-option): Grab a value for the option when it takes
either an optional or required value.
A new argument-processing package from Russ McManus.
* getopt-long.scm: New file.
* Makefile.am (ice9_sources): Added getopt-long.scm.
* Makefile.in: Regenerated.