patch 9.0.0067: cannot show virtual text

Problem:    Cannot show virtual text.
Solution:   Initial changes for virtual text support, using text properties.
diff --git a/src/proto/textprop.pro b/src/proto/textprop.pro
index 72a900b..4a6bab3 100644
--- a/src/proto/textprop.pro
+++ b/src/proto/textprop.pro
@@ -2,7 +2,7 @@
 int find_prop_type_id(char_u *name, buf_T *buf);
 void f_prop_add(typval_T *argvars, typval_T *rettv);
 void f_prop_add_list(typval_T *argvars, typval_T *rettv);
-void prop_add_common(linenr_T start_lnum, colnr_T start_col, dict_T *dict, buf_T *default_buf, typval_T *dict_arg);
+int prop_add_common(linenr_T start_lnum, colnr_T start_col, dict_T *dict, buf_T *default_buf, typval_T *dict_arg);
 int get_text_props(buf_T *buf, linenr_T lnum, char_u **props, int will_change);
 int count_props(linenr_T lnum, int only_starting);
 int find_visible_prop(win_T *wp, int type_id, int id, textprop_T *prop, linenr_T *found_lnum);