Add support for escaping hex colour codes

This is not widely supported but we should have an escape regardless.

docs/conf/inspircd.conf.example

@@ -366,6 +366,7 @@
          # used in your MOTD:
          # Bold:          \b
          # Color:         \c<fg>[,<bg>]
+         # Hex Color:     \h<fg>[,<bg>]
          # Italic:        \i
          # Monospace:     \m  (not widely supported)
          # Reset:         \x

src/helperfuncs.cpp

@@ -158,6 +158,7 @@ void InspIRCd::ProcessColors(file_cache& input)
 	} special[] = {
 		special_chars("\\b", "\x02"), // Bold
 		special_chars("\\c", "\x03"), // Color
+		special_chars("\\h", "\x04"), // Hex Color
 		special_chars("\\i", "\x1D"), // Italic
 		special_chars("\\m", "\x11"), // Monospace
 		special_chars("\\r", "\x16"), // Reverse