patch 7.4.1892
Problem:    balloon eval only gets the window number, not the ID.
Solution:   Add v:beval_winid.
diff --git a/src/gui_beval.c b/src/gui_beval.c
index 9a945bc..4525dde 100644
--- a/src/gui_beval.c
+++ b/src/gui_beval.c
@@ -61,6 +61,7 @@
 
 	    set_vim_var_nr(VV_BEVAL_BUFNR, (long)wp->w_buffer->b_fnum);
 	    set_vim_var_nr(VV_BEVAL_WINNR, winnr);
+	    set_vim_var_nr(VV_BEVAL_WINID, wp->w_id);
 	    set_vim_var_nr(VV_BEVAL_LNUM, (long)lnum);
 	    set_vim_var_nr(VV_BEVAL_COL, (long)(col + 1));
 	    set_vim_var_string(VV_BEVAL_TEXT, text, -1);