patch 8.2.0972: Vim9 script variable declarations need a type

Problem:    Vim9 script variable declarations need a type.
Solution:   Make "let var: type" declare a script-local variable.
diff --git a/src/globals.h b/src/globals.h
index e5dcb7b..f0b75e5 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1785,6 +1785,8 @@
 EXTERN char e_no_white_before[] INIT(= N_("E1068: No white space allowed before '%s'"));
 
 EXTERN char e_lock_unlock[]	INIT(= N_("E940: Cannot lock or unlock variable %s"));
+EXTERN char e_const_req_value[] INIT(= N_("E1021: const requires a value"));
+EXTERN char e_type_req[]	INIT(= N_("E1022: type or initialization required"));
 #endif
 #if defined(FEAT_GUI) || defined(FEAT_TERMGUICOLORS)
 EXTERN char e_alloc_color[]	INIT(= N_("E254: Cannot allocate color %s"));