Allow MSXbin to write size of the imported data as a constant

[pvmm]

For instance:

const unsigned char data[] = {
        0x43, 0x33, 0x33, 0x34, 0x43, 0x33, 0x33, 0x34, 0x43, 0x33, 0x33, 0x34, 
        0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF 
};
const unsigned int data_length = 24;

[aoineko-fr]

Why don't just use sizeof(data)?

[pvmm]

Eh, I used the wrong example here. I think it would be useful for generated assembly code when you are generating code on the fly, so you are not expected to edit the file manually and add something like:
length equ $-data