[BUILD] add default path for searching libraries

- on debian systems, most libraries are in /usr/lib and /usr/include so
  adding this as default would allow for very simple cmake commands

Author: hroest

cmake/setup_lib_find_paths.cmake

@@ -48,7 +48,7 @@ if("${CMAKE_FIND_ROOT_PATH}" STREQUAL "")
   else()
 		# Append a few unusual default search directories for convenience
 		# if no FIND ROOT PATH was specified.
-		list(APPEND CONTRIB_DIR /opt/local /usr/local)
+		list(APPEND CONTRIB_DIR /opt/local /usr/local /usr)
 	endif()
 endif()