Refactor the command line parser so that it uses options_description,

as opposed to having his own data structures. Clean up option description
classes a bit, removing unneeded methods. Remove support for 'implicit'
options.


[SVN r28413]

libs/program_options

@@ -1 +1 @@
-Subproject commit 07778adab7dab8b9ee1e55de4ba1de53dffdd84f
+Subproject commit c984d59de1f3d098df02068ef49d076502285c3f