- cleaned out a large part of unused methods from VMValue.

- keep string registers which are being used as function parameters allocated until after the function call returns. This is for allowing to pass strings by reference which would avoid some costly constructor/destructor loops in the call instruction.

src/scripting/backend/vmbuilder.cpp

@@ -570,6 +570,7 @@ size_t VMFunctionBuilder::Emit(int opcode, int opa, int opb, int opc)
 	assert(opb >= 0);
 	assert(opc >= 0);
 
+	assert(opcode != OP_NOP);
 
 	// The following were just asserts, meaning this would silently create broken code if there was an overflow
 	// if this happened in a release build. Not good.