Attempt to fix .rom directive not suitable for 48kB ROM

[duhow]

Fixes #5

[duhow]

Given the following code:

.page 1
.rom
.size 48
.start INIT
.db "PAGE 1"
INIT:
ret

.page 2
.db "PAGE 2"

.page 0
.db "PAGE 0"
; EOF

This will succeed for the following request:

• Page 0 has no cartridge header
• Page 1 has cartridge header ("AB" + INIT + padding up to 16 bytes)

⚠️ BUT! - INIT code starts at 0x4010, not expected 0x4016 as requested.
By changing the .db input BEFORE doing .start, it works.

 .page 1
 .rom
 .size 48
-.start INIT
 .db "PAGE 1"
+.start INIT
 INIT:
 ret

[Fubukimaru]

Good work :)