patch 8.2.1329: Vim9: cannot define global function inside :def function

Problem:    Vim9: cannot define global function inside :def function.
Solution:   Assign to global variable instead of local. (closes #6584)
diff --git a/src/proto/misc2.pro b/src/proto/misc2.pro
index e1e20aa..d55fc31 100644
--- a/src/proto/misc2.pro
+++ b/src/proto/misc2.pro
@@ -56,6 +56,7 @@
 int vim_isspace(int x);
 void ga_clear(garray_T *gap);
 void ga_clear_strings(garray_T *gap);
+int ga_copy_strings(garray_T *from, garray_T *to);
 void ga_init(garray_T *gap);
 void ga_init2(garray_T *gap, int itemsize, int growsize);
 int ga_grow(garray_T *gap, int n);