#2627 Let it be known what pgen generates

Include/graminit.h

+/* Generated by Parser/pgen */
+
 #define single_input 256
 #define file_input 257
 #define eval_input 258

Parser/printgrammar.c

@@ -13,6 +13,7 @@ static void printlabels(grammar *, FILE *);
 void
 printgrammar(grammar *g, FILE *fp)
 {
+	fprintf(fp, "/* Generated by Parser/pgen */\n\n");
 	fprintf(fp, "#include \"pgenheaders.h\"\n");
 	fprintf(fp, "#include \"grammar.h\"\n");
 	printdfas(g, fp);
@@ -31,6 +32,8 @@ printnonterminals(grammar *g, FILE *fp)
 	dfa *d;
 	int i;
 	
+	fprintf(fp, "/* Generated by Parser/pgen */\n\n");
+	
 	d = g->g_dfa;
 	for (i = g->g_ndfas; --i >= 0; d++)
 		fprintf(fp, "#define %s %d\n", d->d_name, d->d_type);

Python/graminit.c

+/* Generated by Parser/pgen */
+
 #include "pgenheaders.h"
 #include "grammar.h"
 static arc arcs_0_0[3] = {