[vala/staging] Drop leftover deprecated syntax support of += and -= for dynamic signals

[Rico Tzschichholz <ricotz src gnome org>]

commit b9b6f398f625d0fac9f89eab28834c611e5d429d
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Wed Jan 2 18:41:37 2019 +0100

    Drop leftover deprecated syntax support of += and -= for dynamic signals
    
    See https://gitlab.gnome.org/GNOME/vala/issues/676

 vala/valamemberaccess.vala | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)
---
diff --git a/vala/valamemberaccess.vala b/vala/valamemberaccess.vala
index 6690c62b7..09faed946 100644
--- a/vala/valamemberaccess.vala
+++ b/vala/valamemberaccess.vala
@@ -403,16 +403,7 @@ public class Vala.MemberAccess : Expression {
                                        }
                                } else if (parent_node is Assignment) {
                                        var a = (Assignment) parent_node;
-                                       if (a.left == this
-                                           && (a.operator == AssignmentOperator.ADD
-                                               || a.operator == AssignmentOperator.SUB)) {
-                                               // dynamic signal
-                                               var s = new DynamicSignal (inner.value_type, member_name, new 
VoidType (), source_reference);
-                                               s.handler = a.right;
-                                               s.access = SymbolAccessibility.PUBLIC;
-                                               dynamic_object_type.type_symbol.scope.add (null, s);
-                                               symbol_reference = s;
-                                       } else if (a.left == this) {
+                                       if (a.left == this) {
                                                // dynamic property assignment
                                                var prop = new DynamicProperty (inner.value_type, 
member_name, source_reference);
                                                prop.access = SymbolAccessibility.PUBLIC;