Literals on byte reciving mnemonics don't work

Consider
```asm
LDCH =4
```

that gets assembled to:
```asm
LDCH f
f WORD 4
```

but that doesn't as MSB is 0. The solution is to either emit `BYTE`:
```asm
LDCH f
f BYTE 4
```
or:
```asm
	LDCH f
f	WORD 4
f2	EQU f+2
```
(because `LDCH f+2` does not work).

All device mnemonics are affected too.
