incorrect write_json()\read_json() for not latin1 charset.

[shirshov evgeny <381677383@…>]

use MSVC compiler.

property_tree::ptree pt_1; // use symbol > 127            
property_tree::write_json("file", pt_1);

property_tree::ptree pt_2;            
property_tree::read_json("file", pt_2);
pt_1 != pt_2;  !!!!!

for property_tree::wptree all correct.

in msvc char = signed int8.
typedef basic_string<char, char_traits<char>, allocator<char> >

string;

path: file boost\property_tree\detail\json_parser_write.hpp

template<class Ch> std::basic_string<Ch> create_escapes(const std::basic_string<Ch> &s)

         typename std::basic_string<Ch>::const_iterator e = s.end();
         while (b != e)
         {
+            auto bb = static_cast<make_unsigned<Ch>::type>(*b);
             // This assumes an ASCII superset. But so does everything in PTree.
             // We escape everything outside ASCII, because this code can't
             // handle high unicode characters.
-            if (*b == 0x20 || *b == 0x21 || (*b >= 0x23 && *b <= 0x2E) ||
-                (*b >= 0x30 && *b <= 0x5B) || (*b >= 0x5D && *b <= 0xFF))
+            if (bb == 0x20 || bb == 0x21 || (bb >= 0x23 && bb <= 0x2E) ||
+                (bb >= 0x30 && bb <= 0x5B) || (bb >= 0x5D && bb <= 0xFF))

[Sebastian Redl]

Reported again (and fixed there) in bug 10820.