* src/scan-gram.l, src/reader.h (scanner_last_string_free):

Restore.
* src/scan-gram.l (last_string): Is global to the file, not to
yylex.
* src/parse-gram.y (input): Don't append the epilogue here,
(epilogue.opt): do it here, and free the scanner's obstack.
* src/reader.c (epilogue_set): Rename as...
(epilogue_augment): this.
* data/c.m4 (b4_epilogue): Defaults to empty.

src/scan-gram.l

@@ -142,6 +142,10 @@ extend_location (location_t *loc, char const *token, int size)
 
 static struct obstack string_obstack;
 
+/* A string representing the most recently saved token.  */
+static char *last_string;
+
+
 #define YY_OBS_GROW   \
   obstack_grow (&string_obstack, yytext, yyleng)
 
@@ -154,6 +158,11 @@ static struct obstack string_obstack;
 #define YY_OBS_FREE \
   obstack_free (&string_obstack, last_string)
 
+void
+scanner_last_string_free (void)
+{
+  YY_OBS_FREE;
+}
 
 /* Within well-formed rules, RULE_LENGTH is the number of values in
    the current rule so far, which says where to find `$0' with respect
@@ -199,9 +208,6 @@ splice	 (\\[ \f\t\v]*\n)*
   /* Scanner context when scanning C code.  */
   int c_context IF_LINT (= 0);
 
-  /* A string representing the most recently saved token.  */
-  char *last_string;
-
   /* At each yylex invocation, mark the current position as the
      start of the next token.  */
   YY_STEP;