Edit NSF export format to allow adding more effects #46
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Previously, NSF export wrote command numbers as even bytes, and used them directly as indexes into an array of 2-byte command handler addresses. However we ran out of even bytes in the range of bytes interpreted as commands [$80 .. $E0). Now, each command number is an arbitrary byte, and the driver multiplies commands by 2 (dropping the high bit), turning them into valid indices into an array of 2-byte command handler addresses. Now we have twice as many slots available for effects/commands.
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Previously, NSF export wrote command numbers as even bytes, and used them directly as indexes into an array of 2-byte command handler addresses. However we ran out of even bytes in the range of bytes interpreted as commands
[$80 .. $E0), meaning there's no unused IDs to use for new effects.Now, each command number is an arbitrary byte, and the driver multiplies commands by 2 (dropping the high bit), turning them into valid indices into an array of 2-byte command handler addresses. Now we have twice as many slots available for effects/commands. This enables adding more effects into the NSF driver, both effects implemented in the tracker but missing from NSF export, and future effects.