/* Is this interval writable? Replace later with cache access. */
#define INTERVAL_WRITABLE_P(i) \
(i && (NILP (textget ((i)->plist, Qread_only)) \
+ || !NILP (textget ((i)->plist, Qinhibit_read_only)) \
|| ((CONSP (Vinhibit_read_only) \
? !NILP (Fmemq (textget ((i)->plist, Qread_only), \
Vinhibit_read_only)) \