zasm: fix first pass inversion bug

Also, confirm in tests that we can refer to other symbols in `.equ`.

apps/zasm/directive.asm

@@ -50,7 +50,7 @@ handleDW:
 
 handleEQU:
 	call	zasmIsFirstPass
-	jr	z, .begin
+	jr	nz, .begin
 	; first pass? .equ are noops
 	xor	a
 	ret
@@ -74,7 +74,6 @@ handleEQU:
 	call	toWord
 	call	readWord
 	ld	hl, scratchpad
-	ld	a, (hl)
 	call	parseNumberOrSymbol
 	jr	nz, .error
 	ld	hl, DIREC_SCRATCHPAD

apps/zasm/tests/test1.asm

@@ -11,5 +11,6 @@ label2:
 	.dw	3742
 	.dw	0x3742
 	ld	a, (label1)
-.equ	foobar	0x1234
-	ld	hl, foobar
+.equ	foo	0x1234
+.equ	bar	foo
+	ld	hl, bar