Sound IDs equated

Equated sound IDs and applied them to every appropriate area I could
find. The Sound Flag slots were missing a number of equates ($E2, $E3,).
I equated some IDs that already had available constants, but weren't
modified to use them for whatever reason. There are too many non-equated
instances to list here.

Pointed out sound driver slot allocation bugs with attached fixes under
Sound_ChkValue.

Corrected LevSel_NoCheat's comments and expanded on the nature of a
group of instructions.

Fixes tested and confirmed to work. Bugs tested and confirmed to cause crashes. Bit-perfect build (by ASM68K's standards).