Support distinct project and library makefile includes.

Makefile
makefiles/include.mk
makefiles/lint/include.mk
makefiles/python/include.mk
---------------------------
  O Library makefiles only require an include directory var.
  o Project makefiles require two vars, one for derived paths (TOP=).
  o Infer library makefile path from the included makefile.
  o Maintain MAKEDIR= and ONF_MAKEDIR= so caller can selectively
    include what they want to use.

Change-Id: Id1a6d76a278edc130729dd641688c9e5793e90f4
diff --git a/makefiles/python/include.mk b/makefiles/python/include.mk
index 24f3426..70b5ca1 100644
--- a/makefiles/python/include.mk
+++ b/makefiles/python/include.mk
@@ -19,9 +19,9 @@
 # -----------------------------------------------------------------------
 
 ifdef PYTHON_FILES
-  include $(ONF_MAKE)/python/test/include.mk
+  include $(ONF_MAKEDIR)/python/test/include.mk
 else
-  include $(ONF_MAKE)/python/test/include.mk
+  include $(ONF_MAKEDIR)/python/test/include.mk
 endif
 
 # [EOF]