Add support for flex 2.6.0

* src/parse/asm-scan.ll.gen.py: here.

src/parse/asm-scan.ll.gen.py

@@ -276,10 +276,12 @@ print ("""
 /* Depending upon the version of Flex (> 2.5.4), there might be a
    function to reclaim all the memory Flex has allocated.  If not,
    simulate it. */
-#if !(   YY_FLEX_MAJOR_VERSION >= 2             \
-      && YY_FLEX_MINOR_VERSION >= 5             \
-      && defined YY_FLEX_SUBMINOR_VERSION       \
-      && YY_FLEX_SUBMINOR_VERSION >= 5)
+#if !((YY_FLEX_MAJOR_VERSION >= 2             \
+       && YY_FLEX_MINOR_VERSION >= 6) ||      \
+      (YY_FLEX_MAJOR_VERSION >= 2             \
+       && YY_FLEX_MINOR_VERSION >= 5          \
+       && defined YY_FLEX_SUBMINOR_VERSION    \
+       && YY_FLEX_SUBMINOR_VERSION >= 5))
 static void
 yylex_destroy(void)
 {