patch 8.1.1406: popup_hide() and popup_show() not implemented yet

Problem:    popup_hide() and popup_show() not implemented yet.
Solution:   Implement the functions.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 3256b22..b15e74d 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -810,6 +810,8 @@
 #ifdef FEAT_TEXT_PROP
     {"popup_close",	1, 1, f_popup_close},
     {"popup_create",	2, 2, f_popup_create},
+    {"popup_hide",	1, 1, f_popup_hide},
+    {"popup_show",	1, 1, f_popup_show},
 #endif
 #ifdef FEAT_FLOAT
     {"pow",		2, 2, f_pow},