compel: plugins,fds -- Unify prototypes

 - Declare send_fds, recv_fds in sch.h, these
   are prototypes used in both compel and criu
 - Drop old protos from plugin-fds.h uapi file
 - Drop old code from fds.c source
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

include/common/scm.h

@@ -2,6 +2,8 @@
 #define __COMMON_SCM_H__
 
 #include <stdint.h>
+#include <stdbool.h>
+#include <sys/un.h>
 
 /*
  * Because of kernel doing kmalloc for user data passed
@@ -41,4 +43,13 @@ struct scm_fdset {
 #define F_GETOWNER_UIDS	17
 #endif
 
+extern int send_fds(int sock, struct sockaddr_un *saddr, int len,
+		    int *fds, int nr_fds, bool with_flags);
+
+#ifdef SCM_FDSET_HAS_OPTS
+extern int recv_fds(int sock, int *fds, int nr_fds, struct fd_opts *opts);
+#else
+extern int recv_fds(int sock, int *fds, int nr_fds, char *opts);
+#endif
+
 #endif