Add some more tests, and fix some existing ones

test/asm/use-purged-symbol.asm

@@ -0,0 +1,26 @@
+SECTION "test", ROM0
+
+MACRO m
+ENDM
+PURGE m
+	m
+
+DEF argi EQU 1
+MACRO m2
+	println "(\<argi>)!"
+ENDM
+	PURGE argi
+	m2 hello
+
+DEF n EQU argi
+
+PRINTLN "({argi})"
+
+Label::
+PURGE Label
+DEF x = Label
+DEF x = BANK(Label)
+
+Label2::
+PURGE Label2
+DEF x EQUS SECTION(Label2) ; fatal