MFC r298519:
Fix streams and svr4 module dependency. Both modules are complaining about
undefined symbol svr4_delete_socket which was moved from streams to the svr4 module
in r160558 that created a two-way dependency between them.
MFC r298520:
Allow to build svr4 module with SYSV support separatelly from the kernel build.
PR: 208464
Reported by: Kristoffer Eriksson