Fix a regression -- the if the 'style' argument to parse_command_line

function was zero, it was interpreted as no style is suppored. Previously,
it was interpreted as default_styles. Also, remove 'style' argument from
'cmdline' constructors.


[SVN r28500]

libs/program_options

@@ -1 +1 @@
-Subproject commit efc9712f70a07ba15e1c84cb4e2e5e4d573fd1ca
+Subproject commit d4748e81531c4025fd50f808f872ab0d6c5495eb