[Minor] Update embedded doxydown

 - To fix nested lists

doc/doxydown/doxydown.pl

@@ -16,17 +16,17 @@ my %languages = (
     c => {
         start  => qr/^\s*\/\*\*\*(?:\s*|(\s+\S.+\s*))$/,
         end    => qr/^\s*\*+\/\s*$/,
-        filter => qr/^(?:\s*\*+\s*)?(\s*\S.+)\s*$/,
+        filter => qr/^(?:\s*\*+\s?)?(\s*\S.+)\s*$/,
     },
     lua => {
         start  => qr/^\s*\--(?:\[\[\[+|-+)\s*$/,
         end    => qr/^\s*--(:?\]\]+|-+)\s*$/,
-        filter => qr/^(?:\s*--!?\s)?(\s*\S.+)\s*$/,
+        filter => qr/^(?:\s*--!?\s?)?(\s*\S.+)\s*$/,
     },
     sql => {
         start  => qr/^\s*\--(?:\[\[+|-+)\s*$/,
         end    => qr/^\s*--(:?\]\]+|-+)\s*$/,
-        filter => qr/^(?:\s*--\s)?(\s*\S.+)\s*$/,
+        filter => qr/^(?:\s*--\s?)?(\s*\S.+)\s*$/,
     },
     pl => {
         start  => qr/^\s*\##+\s*$/,