Fix 'unknown option' error for two successive calls to 'store'.

The bug triggered if
- we store two parsed_option object into variables_map
- the options descriptions associated with those parsed_option objects
  are different
- an option present in first parser_option object is not declared in
  second options_description.

The problem was that on the second 'store' call we went over all
stored options, trying to get their description from the *second*
options description object.

Thanks to Hartmut Kaiser for the bug report.


[SVN r28685]

libs/program_options

@@ -1 +1 @@
-Subproject commit dc9097c3d06192c4c7fdf78b25d3c748837d43aa
+Subproject commit 9a149beb76ceca164204ef8653be47e404d19936