[GSC] --pad-oper issue with modulo

One more issue related to GSC language. I can't use --pad-oper because the language has a double use case for the % operator. It can also be used as anim variable names. Here are some example in the ways it can be used:

level.shockbox_anim["on"] = %fxanim_zom_al_shock_box_on_anim;
self setanim( %o_riot_stand_deploy, 1.0, 0.0, 1.0 );
self buildfacestate( "face_casual", 1, -1, 0, "basestate", %pf_casual_idle );

Basically, whenever the % is preceded by a =, (, or , then it should not treat it as an oper.