Slight improvement to cursor blink timing: since the cursor doesn't

blink when the window doesn't have focus, we don't schedule blink
timers at that point either.

Infrastructure change: term->has_focus should now not be written
directly from outside terminal.c. Instead, use the function
term_set_focus, which will sort out the blink timers as well.

[originally from svn r4911]

putty.h

@@ -664,6 +664,7 @@ void term_provide_resize_fn(Terminal *term,
 			    void (*resize_fn)(void *, int, int),
 			    void *resize_ctx);
 void term_provide_logctx(Terminal *term, void *logctx);
+void term_set_focus(Terminal *term, int has_focus);
 
 /*
  * Exports from logging.c.