Add COMMENT about GRAMMAR suffixes

Author: ntrel

dlang.org.ddoc

@@ -185,6 +185,7 @@ GLOSSARY = $(HTTP dlang.org/spec/glossary.html#$0, $0)
 GLOSSARY2 = $(HTTP dlang.org/spec/glossary.html#$1, $2)
 GNAME=<a id="$0">$(SPANC gname, $0)</a>
 _=
+$(COMMENT GRAMMAR invocations will appear in spec/grammar.html, but NOT the suffixed macros)
 GRAMMAR=$(TC pre, bnf notranslate, $0)
 GRAMMAR_INFORMATIVE=$(GRAMMAR $0)
 GRAMMAR_LEX=$(GRAMMAR $0)