Merge pull request swiftlang#29 from seabaylea/queue_concurrent

Initialise dispatch_queue_attr_concurrent on Linux

Author: MadCoder

src/init.c

@@ -260,6 +260,13 @@ const struct dispatch_queue_attr_s _dispatch_queue_attrs[]
 	DISPATCH_QUEUE_ATTR_QOS_INITIALIZER(USER_INTERACTIVE),
 };
 
+// _dispatch_queue_attr_concurrent is aliased using libdispatch.aliases
+// and the -alias_list linker option on Darwin but needs to be done manually
+// for other platforms.
+#ifndef __APPLE__
+extern struct dispatch_queue_attr_s _dispatch_queue_attr_concurrent
+	__attribute__((__alias__("_dispatch_queue_attrs")));
+#endif
 
 #pragma mark -
 #pragma mark dispatch_vtables