Allow 'make-string' callers force creation of multibyte strings

Allow 'make-string' callers force creation of multibyte strings

* src/alloc.c (Fmake_string): Accept additional argument
MULTIBYTE, and produce a multibyte string if it is non-nil.
(make_event_array):
* src/lread.c (read0):
* src/editfns.c (Ftranslate_region_internal):
* src/coding.c (Fdefine_coding_system_internal):
* src/cmds.c (internal_self_insert):
* src/xdisp.c (build_desired_tool_bar_string)
(store_mode_line_string): All C callers changed.

* doc/lispref/strings.texi (Creating Strings): Document the new
optional argument.

* etc/NEWS: Mention the new optional argument.

* lisp/ruler-mode.el (ruler-mode-ruler): Call make-string with the
3rd argument non-nil.