patch 9.0.1459: typo in name of type

Problem:    Typo in name of type.
Solution:   Change funccal_T to funccall_T. (closes #12265)
diff --git a/src/strings.c b/src/strings.c
index 2099794..7c868bf 100644
--- a/src/strings.c
+++ b/src/strings.c
@@ -902,7 +902,7 @@
     // set_vim_var_nr() doesn't set the type
     set_vim_var_type(VV_KEY, VAR_NUMBER);
 
-    // Create one funccal_T for all eval_expr_typval() calls.
+    // Create one funccall_T for all eval_expr_typval() calls.
     fc = eval_expr_get_funccal(expr, &newtv);
 
     ga_init2(&ga, sizeof(char), 80);
@@ -981,7 +981,7 @@
     else
 	copy_tv(&argvars[2], rettv);
 
-    // Create one funccal_T for all eval_expr_typval() calls.
+    // Create one funccall_T for all eval_expr_typval() calls.
     fc = eval_expr_get_funccal(expr, rettv);
 
     for ( ; *p != NUL; p += len)