Fix build errors in Zoom/VoiceOver patch

- Remove 'extern Lisp_Object last_command_event' - last_command_event
  is a macro in globals.h (expands to globals.f_last_command_event),
  so an extern declaration conflicts with the existing
  'extern struct emacs_globals globals'
- Replace invalid C escape sequences '\C-n' and '\C-p' with
  ('n' & 0x1f) and ('p' & 0x1f) respectively

patches/0001-ns-implement-AXBoundsForRange-for-macOS-Zoom-cursor-.patch

@@ -585,8 +585,6 @@ index 932d209..da40369 100644
  }
  
 -- (void) noteUserCancelledSelection
-+extern Lisp_Object last_command_event;
-+
 +static bool
 +ns_ax_event_is_ctrl_n_or_p (int *which)
  {
@@ -603,13 +601,13 @@ index 932d209..da40369 100644
  
 -  [NSApp stop: self];
 +  EMACS_INT c = XFIXNUM (ev);
-+  if (c == '\C-n')
++  if (c == ('n' & 0x1f))
 +    {
 +      if (which)
 +	*which = 1;
 +      return true;
 +    }
-+  if (c == '\C-p')
++  if (c == ('p' & 0x1f))
 +    {
 +      if (which)
 +	*which = -1;