Introduce VIR_STREAM_RECV_STOP_AT_HOLE flag

Add a new flag to virStreamRecvFlags in order to handle being able to
stop reading from the stream so that the consumer can generate a "hole"
in stream target. Generation of a hole replaces the need to receive and
handle a sequence of zero bytes for sparse stream targets.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

include/libvirt/libvirt-stream.h

@@ -45,6 +45,10 @@ int virStreamRecv(virStreamPtr st,
                   char *data,
                   size_t nbytes);
 
+typedef enum {
+    VIR_STREAM_RECV_STOP_AT_HOLE = (1 << 0),
+} virStreamRecvFlagsValues;
+
 int virStreamRecvFlags(virStreamPtr st,
                        char *data,
                        size_t nbytes,