Provide macros [GS]ET_COMM_ALIGN if it's missing (<= 10.4).

--- ld64-241.9/src/ld/parsers/macho_relocatable_file.cpp	2015-01-22 22:23:11.000000000 +0100
+++ ld64-241.9/src/ld/parsers/macho_relocatable_file.cpp	2015-01-22 22:28:03.000000000 +0100
@@ -51,6 +51,10 @@
 #include "macho_relocatable_file.h"
 
 
+/* missing on < 10.5 */
+#if !defined(GET_COMM_ALIGN)
+#define GET_COMM_ALIGN(n_desc) (((n_desc) >> 8) & 0x0f)
+#endif
 
 extern void throwf(const char* format, ...) __attribute__ ((noreturn,format(printf, 1, 2)));
 extern void warning(const char* format, ...) __attribute__((format(printf, 1, 2)));
--- Gentoo/tmp/var/tmp/portage/sys-devel/binutils-apple-6.1/work/ld64-241.9/src/ld/LinkEditClassic.hpp	2015-01-22 22:29:14.000000000 +0100
+++ ld64-241.9/src/ld/LinkEditClassic.hpp	2015-01-22 22:31:23.000000000 +0100
@@ -39,6 +39,12 @@
 #define UNORDERED_MAP unordered_map
 #endif
 
+#if !defined(SET_COMM_ALIGN)
+/* missing on < 10.5 */
+#define SET_COMM_ALIGN(n_desc,align) \
+    (n_desc) = (((n_desc) & 0xf0ff) | (((align) & 0x0f) << 8))
+#endif
+
 #include "Options.h"
 #include "ld.hpp"
 #include "Architectures.hpp"