improve the Space text convertion methods

Read the whole character from a multibyte string (as int/char32_t) and
then check if it needs to be escaped. Also don't use a tmp stream object
when serializing between wide/char strings.

while here:
- add try_esc_to_space(...) global function
- add wide_to_output_function(const wchar_t * str, size_t len, OutputFunction output_function, int mode)
- add wide_to_output_function(const wchar_t * str, OutputFunction output_function, int mode)

src/convert/misc.cpp

@@ -525,6 +525,58 @@ bool try_esc_to_html(char32_t c, pt::Stream & out)
 }
 
 
+bool try_esc_to_space(char32_t c, pt::Stream & out)
+{
+	bool status = false;
+
+	switch(c)
+	{
+	case 0:
+		out << '\\';
+		out << 'u' << '{' << '0' << '}';
+		status = true;
+		break;
+
+	case '\r':	// 13
+		out << '\\';
+		out << 'r';
+		status = true;
+		break;
+
+	case '\n': // 10
+		out << '\\';
+		out << 'n';
+		status = true;
+		break;
+
+	case '\\':
+		out << '\\';
+		out << '\\';
+		status = true;
+		break;
+
+	case '"':
+		out << '\\';
+		out << '\"';
+		status = true;
+		break;
+
+	case '\b': // 8
+		out << '\\';
+		out << 'b';
+		status = true;
+		break;
+
+	case '\f': // 12
+		out << '\\';
+		out << 'f';
+		status = true;
+		break;
+	}
+
+	return status;
+}
+
 
 }