escape first dash ('-') in double-dashes ('--') found in doxygen comments

This should prevent doxygen from generating bad documentation HTML pages
containing '<ndash></ndash>' where those double-dashes should be.

include/boost/program_options/eof_iterator.hpp

@@ -12,7 +12,7 @@ namespace boost {
 
     /** The 'eof_iterator' class is useful for constructing forward iterators
         in cases where iterator extract data from some source and it's easy
-        to detect 'eof' -- i.e. the situation where there's no data. One
+        to detect 'eof' \-- i.e. the situation where there's no data. One
         apparent example is reading lines from a file.
 
         Implementing such iterators using 'iterator_facade' directly would

include/boost/program_options/option.hpp

@@ -15,7 +15,7 @@ namespace boost { namespace program_options {
 
     /** Option found in input source.
         Contains a key and a value. The key, in turn, can be a string (name of
-        an option), or an integer (position in input source) -- in case no name
+        an option), or an integer (position in input source) \-- in case no name
         is specified. The latter is only possible for command line.
         The template parameter specifies the type of char used for storing the
         option's value.

include/boost/program_options/options_description.hpp

@@ -41,7 +41,7 @@ namespace program_options {
         are used only to validate input. Second affect interpretation of the
         option, for example default value for it or function that should be
         called  when the value is finally known. Routines which perform parsing
-        never use second kind of properties -- they are side effect free.
+        never use second kind of properties \-- they are side effect free.
         @sa options_description
     */
     class BOOST_PROGRAM_OPTIONS_DECL option_description {
@@ -71,7 +71,7 @@ namespace program_options {
             The 'name' parameter is interpreted by the following rules:
             - if there's no "," character in 'name', it specifies long name
             - otherwise, the part before "," specifies long name and the part
-            after -- short name.
+            after \-- short name.
         */
         option_description(const char* name,
                            const value_semantic* s);

include/boost/program_options/parsers.hpp

@@ -101,14 +101,14 @@ namespace boost { namespace program_options {
 
         The class allows one to specify all the information needed for parsing
         and to parse the command line. It is primarily needed to
-        emulate named function parameters -- a regular function with 5
+        emulate named function parameters \-- a regular function with 5
         parameters will be hard to use and creating overloads with a smaller
         number of parameters will be confusing.
 
         For the most common case, the function parse_command_line is a better
         alternative.
 
-        There are two typedefs -- command_line_parser and wcommand_line_parser,
+        There are two typedefs \-- command_line_parser and wcommand_line_parser,
         for charT == char and charT == wchar_t cases.
     */
     template<class charT>

include/boost/program_options/variables_map.hpp

@@ -164,7 +164,7 @@ namespace boost { namespace program_options {
             which does 'find' in *this. */
         const variable_value& get(const std::string& name) const;
 
-        /** Names of option with 'final' values -- which should not
+        /** Names of option with 'final' values \-- which should not
             be changed by subsequence assignments. */
         std::set<std::string> m_final;