add fasl terminator

While "\44\26\2\f6" currently works as a terminator for non-compressed
fasl streams, the working byte sequence varies as the fasl format
changes. Add "\177" as a simpler and unchanging terminator.

original commit: 332019360491be6cedd2063c9a8056183d764bbb

c/fasl.c

@@ -489,6 +489,8 @@ static ptr fasl_entry(ptr tc, IFASLCODE situation, unbufFaslFile uf) {
       case fasl_type_revisit:
       case fasl_type_visit_revisit:
         break;
+      case fasl_type_terminator:
+        return Seof_object;
       default:
         S_error2("", "malformed fasl-object header (missing situation, got ~s) found in ~a", FIX(ty), uf->path);
         return (ptr)0;

s/cmacros.ss

@@ -462,6 +462,8 @@
 (define-constant fasl-type-phantom 44)
 (define-constant fasl-type-uninterned-symbol 45)
 
+(define-constant fasl-type-terminator 127)
+
 (define-constant fasl-fld-ptr 0)
 (define-constant fasl-fld-u8 1)
 (define-constant fasl-fld-i16 2)