add roundtrip disasm tests for all cpus

test/dasm/6502X-disass.s

@@ -0,0 +1,30 @@
+
+    .setcpu "6502X"
+
+    .repeat 256, cnt
+
+    ; generate a pattern with all opcodes. however, for the full cycle to work,
+    ; we must take care of the "duplicate" opcodes, ie use only the favourite one.
+    .if ((cnt & $0f) = $02)
+    .byte $02   ; all JAM
+    .elseif ((cnt & $1f) = $1a)
+    .byte $ea   ; all NOP
+    .elseif (cnt = $2b)
+    .byte $0b   ; both ANC #imm
+    .elseif (cnt = $89)
+    .byte $80   ; both NOP #imm
+    .elseif (cnt = $eb)
+    .byte $e9   ; both SBC #imm
+    .elseif (cnt = $34) || (cnt = $54) ||  (cnt = $74) ||  (cnt = $d4) || (cnt = $f4)
+    .byte $14   ; all NOP zp, x
+    .elseif (cnt = $3c) || (cnt = $5c) ||  (cnt = $7c) ||  (cnt = $dc) || (cnt = $fc)
+    .byte $1c   ; all NOP abs, x
+    .elseif (cnt = $44) || (cnt = $64)
+    .byte $04   ; all NOP zp
+    .else
+    .byte cnt
+    .endif
+
+    .byte $02, $ea, $00
+
+    .endrepeat