Add tests for explicit definitions of local labels

These check that “Parent.child” may be used in place of “.child”, and that “WrongParent.child” may not be used in the scope of “Parent”.

test/asm/local-wrong-parent.asm

@@ -0,0 +1,6 @@
+SECTION "sec", ROM0
+
+Parent:
+	db 0
+WrongParent.child
+	db 0

test/asm/local-wrong-parent.out

@@ -0,0 +1,3 @@
+ERROR: local-wrong-parent.asm(5):
+	Not currently in the scope of 'WrongParent'
+error: Assembly aborted in pass 1 (1 errors)!

test/asm/remote-local-explicit.asm

@@ -0,0 +1,7 @@
+SECTION "sec", ROM0
+
+Parent:
+Parent.child::
+	db 0
+NotParent:
+	dw Parent.child