Allow to specify how option's value is named in help message.

Fixes #4781.

svn path=/trunk/boost/program_options/; revision=77931
Summary: Moved libs/detail/utf8_codecvt_facet.cpp to boost/detail/utf8_codecvt_facet.ipp
Author: Dave Abrahams <dave@boostpro.com>

svn path=/trunk/libs/program_options/; revision=78081
Include necessary header, don't rely on two-phase lookup not being there.

Fixes #6790.

svn path=/trunk/boost/program_options/; revision=78331
Adjust spelling.

svn path=/trunk/boost/program_options/; revision=78359
Fix compilation error.

Fixes #7049. Patch from Deniz Bahadir.

svn path=/trunk/boost/program_options/; revision=79164
Qualify 'distance' with 'std'.

Fixes #7086.

svn path=/trunk/libs/program_options/; revision=79280
Fix warnings on 64-bit systems.

Closes #7077.

svn path=/trunk/libs/program_options/; revision=79283
Fix indent

svn path=/trunk/libs/program_options/; revision=79289
Really fixes #7049.

svn path=/trunk/boost/program_options/; revision=79477
Revive exception_txt_test. 

Found while working on #8009.

svn path=/trunk/libs/program_options/; revision=82804
Fix report of error for options with dashes.

Fixes #8009.
Patch from Markus Roth.

svn path=/trunk/boost/program_options/; revision=82805