devel/dep: Unbreak on aarch64, take maintainership

http://thunderx1.nyi.freebsd.org/data/head-arm64-default/p520537_s355573/logs/errors/dep-0.5.4.log

github.com/golang/dep/vendor/golang.org/x/sys/unix

vendor/golang.org/x/sys/unix/cap_freebsd.go:18:23: undefined: CAP_RIGHTS_VERSION_00
vendor/golang.org/x/sys/unix/cap_freebsd.go:19:23: undefined: CAP_RIGHTS_VERSION_00
vendor/golang.org/x/sys/unix/cap_freebsd.go:46:21: undefined: CapRights
vendor/golang.org/x/sys/unix/cap_freebsd.go:50:24: undefined: CapRights
vendor/golang.org/x/sys/unix/cap_freebsd.go:55:27: undefined: CapRights
vendor/golang.org/x/sys/unix/cap_freebsd.go:90:29: undefined: CapRights
vendor/golang.org/x/sys/unix/syscall_unix_gc.go:12:6: missing function body
vendor/golang.org/x/sys/unix/syscall_unix_gc.go:13:6: missing function body
vendor/golang.org/x/sys/unix/syscall_unix_gc.go:14:6: missing function body
vendor/golang.org/x/sys/unix/syscall_unix_gc.go:15:6: missing function body

• Unbreak by updating golang.org/x/sys to 33540a1f6037 which brings in necessary freebsd/arm64 bits.
• Take maintainership.