Qualify 'distance' with 'std'.

Fixes #7086.


[SVN r79280]

Author: vprus

src/options_description.cpp

@@ -147,7 +147,7 @@ namespace boost { namespace program_options {
             if (prefix_style == command_line_style::allow_long_disguise)
                 return "-" + m_long_name;
         }
-		// sanity check: m_short_name[0] should be '-' or '/'
+        // sanity check: m_short_name[0] should be '-' or '/'
         if (m_short_name.length() == 2)
         {
             if (prefix_style == command_line_style::allow_slash_for_short)
@@ -469,7 +469,7 @@ namespace boost { namespace program_options {
                     // Take care to never increment the iterator past
                     // the end, since MSVC 8.0 (brokenly), assumes that
                     // doing that, even if no access happens, is a bug.
-                    unsigned remaining = distance(line_begin, par_end);
+                    unsigned remaining = std::distance(line_begin, par_end);
                     string::const_iterator line_end = line_begin + 
                         ((remaining < line_length) ? remaining : line_length);
 
@@ -489,7 +489,7 @@ namespace boost { namespace program_options {
                         {                 
                             // is last_space within the second half ot the 
                             // current line
-                            if (static_cast<unsigned>(distance(last_space, line_end)) < 
+                            if (static_cast<unsigned>(std::distance(last_space, line_end)) < 
                                 (line_length / 2))
                             {
                                 line_end = last_space;