Split b2 dependencies into public and private.

Author: grafikrobot

build.jam

@@ -6,7 +6,6 @@
 require-b2 5.2 ;
 
 constant boost_dependencies :
-    /boost/assert//boost_assert
     /boost/config//boost_config
     /boost/container_hash//boost_container_hash
     /boost/core//boost_core

build/Jamfile.v2

@@ -11,10 +11,15 @@ import config : requires ;
 import feature ;
 import property ;
 
+constant boost_dependencies_private :
+    /boost/assert//boost_assert
+    ;
+
 project
   : common-requirements <library>$(boost_dependencies)
   : requirements
     [ requires cxx11_rvalue_references ]
+    <library>$(boost_dependencies_private)
   : default-build
     <visibility>hidden
   ;