Dereference IDC variable flags

Detailed Description

Passed as 'vref_flags' parameter to deref_idcv()

Macros
#define	VREF_LOOP   0x0000
	dereference until we get a non VT_REF
#define	VREF_ONCE   0x0001
	dereference only once, do not loop
#define	VREF_COPY   0x0002
	copy the result to the input var (v)