Add a simple option parser.
The option parser takes argc, argv, an array of struct option
and a usage string. Each of the struct option elements in the array
describes a valid option, its type and a pointer to the location where the
value is written. The entry point is parse_options(), which scans through
the given argv, and matches each option there against the list of valid
options. During the scan, argv is rewritten to only contain the
non-option command line arguments and the number of these is returned.
Aggregation of single switches is allowed:
-rC0 is the same as -r -C 0 (supposing that -C wants an arg).
Every long option automatically support the option with the same name,
prefixed with 'no-' to unset the switch. It assumes that initial value for
strings are "NULL" and for integers is "0".
Long options are supported either with '=' or without:
--some-option=foo is the same as --some-option foo
Acked-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>