src: wrap MIN definition in infdef

Some platforms already define this; avoid redefining if that's
the case. Found on OpenBSD 5.6.

PR-URL: https://github.com/iojs/io.js/pull/1322
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/node_file.cc

@@ -39,7 +39,9 @@ using v8::Object;
 using v8::String;
 using v8::Value;
 
-#define MIN(a, b) ((a) < (b) ? (a) : (b))
+#ifndef MIN
+# define MIN(a, b) ((a) < (b) ? (a) : (b))
+#endif
 
 #define TYPE_ERROR(msg) env->ThrowTypeError(msg)