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/evalvars.c b/src/evalvars.c
index f2128a6..8a7162c 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -728,8 +728,18 @@
 	else if (expr[0] == '.')
 	    emsg(_("E985: .= is not supported with script version 2"));
 	else if (!ends_excmd2(eap->cmd, arg))
-	    // ":let var1 var2"
-	    arg = list_arg_vars(eap, arg, &first);
+	{
+	    if (current_sctx.sc_version == SCRIPT_VERSION_VIM9)
+	    {
+		// Vim9 declaration ":let var: type"
+		arg = vim9_declare_scriptvar(eap, arg);
+	    }
+	    else
+	    {
+		// ":let var1 var2" - list values
+		arg = list_arg_vars(eap, arg, &first);
+	    }
+	}
 	else if (!eap->skip)
 	{
 	    // ":let"