Disable fine volume slide memory in MOD event decoder

Dennis Lindroos reports:

"I will definitely check it out over the weekend, but after i wrote to you
 about "Velvet Vision" and its fading out "too fast" i had to look at it,
 and i think i know what's happening.

 The fine volume slide EAx and EBx commands in Protracker DO NOT HAVE MEMORY,
 so EB0 should not decrease the volume at all.

 This module loops a series of EB0 EB1 EB0 EB0 EB1 commands and XMP fades
 out on every step but i'm sure this module was intended to fade out much
 slower!"

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Update Unic2 reference data

Remove fine volume slides with zero parameter.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>