Split //aos/common:queues into queues and messages.

These were already distinct concepts; probably makes more sense for them
to be separate. Also it makes it easier for teams to pick and choose
what parts of aos they want to use.

Change-Id: I3e6af61c8e4c1e337714f44b4e7f74a3b8f88060
diff --git a/aos/common/BUILD b/aos/common/BUILD
index 7a15731..0e109fb 100644
--- a/aos/common/BUILD
+++ b/aos/common/BUILD
@@ -144,19 +144,30 @@
 )
 
 cc_library(
-  name = 'queues',
+  name = 'messages',
   srcs = [
-    'queue.cc',
+    'message.cc',
   ],
   hdrs = [
+    'message.h',
+  ],
+  deps = [
+    ':time',
+    ':macros',
+    ':byteorder',
+  ],
+)
+
+cc_library(
+  name = 'queues',
+  srcs = [],
+  hdrs = [
     'queue.h',
   ],
   deps = [
     '//aos/linux_code/ipc_lib:queue',
-    ':time',
-    ':macros',
     '//aos/linux_code:queue',
-    ':byteorder',
+    ':messages',
   ],
 )