Add comments to the auto-generated table

lib/nghttp2_helper.c

@@ -88,6 +88,7 @@ void* nghttp2_memdup(const void* src, size_t n)
   return dest;
 }
 
+/* Generated by gendowncasetbl.py */
 static const int DOWNCASE_TBL[] = {
   0 /* NUL  */, 1 /* SOH  */, 2 /* STX  */, 3 /* ETX  */,
   4 /* EOT  */, 5 /* ENQ  */, 6 /* ACK  */, 7 /* BEL  */,
@@ -329,6 +330,7 @@ void nghttp2_free(void *ptr)
   free(ptr);
 }
 
+/* Generated by gennmchartbl.py */
 static int VALID_HD_NAME_CHARS[] = {
   0 /* NUL  */, 0 /* SOH  */, 0 /* STX  */, 0 /* ETX  */,
   0 /* EOT  */, 0 /* ENQ  */, 0 /* ACK  */, 0 /* BEL  */,
@@ -417,6 +419,7 @@ int nghttp2_check_header_name(const uint8_t *name, size_t len)
   return 1;
 }
 
+/* Generated by genvchartbl.py */
 static int VALID_HD_VALUE_CHARS[] = {
   0 /* NUL  */, 0 /* SOH  */, 0 /* STX  */, 0 /* ETX  */,
   0 /* EOT  */, 0 /* ENQ  */, 0 /* ACK  */, 0 /* BEL  */,