Restructure BUILD

BUILD

+package(default_visibility = ["//visibility:public"])
+
+# Empty cc_library for backward compatibility
 cc_library(
     name = "optonly",
     hdrs = ['src/midout.h'],
     includes = ['src'],
-    visibility = ["//visibility:public"],
+    deprecation = "//brain/midout:optonly is (and was) effectively a no-op, please remove such deps",
 )
 
 cc_library(
     name = "midout",
     srcs = ['src/midout.cpp'],
-    deps = [':optonly'],
-    visibility = ["//visibility:public"],
+    hdrs = ['src/midout.h'],
+    includes = ['src'],
 )
 
 # vim: ft=python