Fix some more socket bugs

- The functions that return a sockaddr now do so the same way the Linux
  Kernel does across platforms, e.g. getpeername(), accept4()

- Socket system calls on Windows will now only check for interrupts when
  a blocking operation needs to be performed.

- Write tests for recvfrom() system call

libc/sock/sockaddr2linux.c

@@ -24,6 +24,8 @@
 #include "libc/sysv/consts/af.h"
 #include "libc/sysv/errfuns.h"
 
+// TODO(jart): DELETE
+
 /**
  * Converts sockaddr_bsd (XNU/BSD) → sockaddr (Linux/Windows).
  */