Improve support for MOTD escape codes.

- Implement escapes for italic, monospace, and strikethrough.
- Use the escape codes in the example MOTDs to demonstrate their
  formatting effects.
- Remove support for octal escape codes. In modern computing octal
  is rarely used and is confusing for users who might confuse it
  for decimal.

docs/conf/inspircd.conf.example

@@ -313,6 +313,18 @@
 
          # Alternate MOTD file for this connect class. The contents of this file are
          # specified using <files secretmotd="filename"> or <execfiles ...>
+         #
+         # NOTE: the following escape sequences for IRC formatting characters can be
+         # used in your MOTD:
+         # Bold:          \b
+         # Color:         \c<fg>[,<bg>]
+         # Italic:        \i
+         # Monospace:     \m  (not widely supported)
+         # Reset:         \x
+         # Strikethrough: \s  (not widely supported)
+         # Underline:     \u
+         # See https://defs.ircdocs.horse/info/formatting.html for more information
+         # on client support for formatting characters.
          motd="secretmotd"
 
          # port: What port range this user is allowed to connect on. (optional)

src/helperfuncs.cpp

@@ -146,19 +146,20 @@ void InspIRCd::ProcessColors(file_cache& input)
 	{
 		std::string character;
 		std::string replace;
-		special_chars(const std::string &c, const std::string &r) : character(c), replace(r) { }
-	}
-
-	special[] = {
-		special_chars("\\002", "\002"),  // Bold
-		special_chars("\\037", "\037"),  // underline
-		special_chars("\\003", "\003"),  // Color
-		special_chars("\\017", "\017"), // Stop colors
-		special_chars("\\u", "\037"),    // Alias for underline
-		special_chars("\\b", "\002"),    // Alias for Bold
-		special_chars("\\x", "\017"),    // Alias for stop
-		special_chars("\\c", "\003"),    // Alias for color
-		special_chars("", "")
+		special_chars(const std::string& c, const std::string& r)
+			: character(c)
+			, replace(r)
+		{
+		}
+	} special[] = {
+		special_chars("\\b", "\x02"), // Bold
+		special_chars("\\c", "\x03"), // Color
+		special_chars("\\i", "\x1D"), // Italic
+		special_chars("\\m", "\x11"), // Monospace
+		special_chars("\\s", "\x1E"), // Strikethrough
+		special_chars("\\u", "\x1F"), // Underline
+		special_chars("\\x", "\x0F"), // Reset
+		special_chars("\\", "")
 	};
 
 	for(file_cache::iterator it = input.begin(), it_end = input.end(); it != it_end; it++)