Fixed PR12389 by making %m/%M use kread() to access memory.

Fixed PR12389 by making %m/%M use kread() to access memory.

* runtime/vsprintf.c (_stp_vsprint_memory): The '%m' and '%M' formatting
  operators use kread() to read memory.
* translate.cxx: Removed all support from the c_unparser class for
  'probe_or_function_needs_deref_fault_handler' processing since it is no
  longer needed.
  (c_unparser::visit_print_format): Removed deref_buffer() call.  Added
  check for c->last_error after print is done.
* runtime/runtime_context.h: New file.
* runtime/vsprintf.h: Ditto.
* runtime/print.c: Removed extra include of vsprintf.c.  Allow use to
  override STP_LOG_BUF_LEN.  Make _stp_print_flush() definitions exactly
  the same between the RELAY_{GUEST,HOST} and normal caes.
* runtime/print.h: Added a few more functions and includes the new
  vsprintf.h file.
* runtime/runtime.h: Includes print.h instead of print.c.  Moved print.c
  and io.c to runtime_context.h.
* runtime/transport/transport.h: Declares '_stp_target'.