patch 8.0.1563: timeout of getwinposx() can be too short

Problem:    Timeout of getwinposx() can be too short. (lilydjwg)
Solution:   Add getwinpos(). (closes #2689)
diff --git a/src/proto/term.pro b/src/proto/term.pro
index 92cb26d..42405dd 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -24,7 +24,7 @@
 void term_append_lines(int line_count);
 void term_delete_lines(int line_count);
 void term_set_winpos(int x, int y);
-int term_get_winpos(int *x, int *y);
+int term_get_winpos(int *x, int *y, varnumber_T timeout);
 void term_set_winsize(int height, int width);
 void term_fg_color(int n);
 void term_bg_color(int n);