eliminate some singletons and static & global variables * pager.h, pager.cc: Rewrite pager_stream and diary_stream classes so they are not singletons. Change all uses. (output_system): New class. * interpreter.h, interpreter.cc (interpreter::m_output_system): New data member. Provide access function. * interpreter-private.h, interpreter-private.cc (__get_output_system__): New function.

--- a/libinterp/corefcn/interpreter.cc	Sat Mar 17 11:59:05 2018 -0500
+++ b/libinterp/corefcn/interpreter.cc	Fri May 25 16:30:01 2018 -0400
@@ -327,6 +327,7 @@
       m_environment (),
       m_help_system (*this),
       m_input_system (*this),
+      m_output_system (*this),
       m_dynamic_loader (*this),
       m_load_path (),
       m_type_info (),