Allowing = for #define

[kinwie]

This is working in sforzando and Cakewalk DropZone, DP and RP

#define $rootkey pitch_keycenter=64
#define $lokey lokey=64
#define $hikey hikey=64

<region>
sample=snare.wav
loop_mode=one_shot
$rootkey
$lokey
$hikey

[jpcima]

There are some worse cases documented in the parser issue #225, on which this must be a subset probably.
The conclusion which I come to, it's that the # elements of SFZ and $ variables should be be preprocessed in a first step.
Then one must take special care to preserve the line and column positions for diagnostics.