Fixed broken build on OS X by conditionally using platform-specific byteswap. Added note about clang incompatibility on OS X and building with gcc. Fixes citusdata#6.

Author: Timon Karnezos

README.markdown

@@ -398,6 +398,10 @@ Or to build with what's on your path, just:
 
         make
 
+If you're building on OS X with `clang` as the default C/C++ compiler, you'll need to specify `gcc` as your compiler:
+
+        make CC=gcc CXX=gcc
+
 Or for the debug build:
 
         DEBUG=1 make

hll.c

@@ -15,7 +15,13 @@
 
 #include <postgres.h>	// Needs to be first.
 
+#if defined(__APPLE__)
+#include <libkern/OSByteOrder.h>
+#define bswap_64 OSSwapInt64
+#else
 #include <byteswap.h>
+#endif
+
 #include <funcapi.h>
 #include <math.h>
 #include <stdlib.h>