mescc: Tinycc support: empty for.

* module/language/c99/compiler.mes (test-jump-label->info): Handle
  empty expression.
* make.scm (add-tcc-test "45_empty_for"): Test it.

make.scm

@@ -310,7 +310,7 @@ exec ${GUILE-guile} --no-auto-compile -L . -L guile -C . -C guile -s "$0" ${1+"$
    ;;"42_function_pointer"     ; f* functions
    "43_void_param"
    "44_scoped_declarations"
-   ;; "45_empty_for"           ; unsupported
+   "45_empty_for"           ; unsupported
    ;;"46_grep"                 ; f* functions
    "47_switch_return"
    "48_nested_break"

module/language/c99/compiler.mes

@@ -1363,6 +1363,7 @@
                                   jump-text)))))
   (lambda (o)
     (pmatch o
+      ((expr) info)
       ;; unsigned
       ;; ((le ,a ,b) ((jump i386:jump-ncz) o)) ; ja
       ;; ((lt ,a ,b) ((jump i386:jump-nc) o))  ; jae