Add SEEK_DATA and SEEK_HOLE constants to FreeBSD and DragonFlyBSD

src/unix/bsd/freebsdlike/mod.rs

@@ -264,6 +264,8 @@ pub const EOF: ::c_int = -1;
 pub const SEEK_SET: ::c_int = 0;
 pub const SEEK_CUR: ::c_int = 1;
 pub const SEEK_END: ::c_int = 2;
+pub const SEEK_DATA: ::c_int = 3;
+pub const SEEK_HOLE: ::c_int = 4;
 pub const _IOFBF: ::c_int = 0;
 pub const _IONBF: ::c_int = 2;
 pub const _IOLBF: ::c_int = 1;