updated for version 7.4.056
Problem:    Mac: Compilation problem with OS X 10.9 Mavericks.
Solution:   Include AvailabilityMacros.h when available. (Kazunobu Kuriyama)
diff --git a/src/version.c b/src/version.c
index 184aee7..c682508 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    56,
+/**/
     55,
 /**/
     54,