[MEDIUM] remove TCP_CORK and make use of MSG_MORE instead

send() supports the MSG_MORE flag on Linux, which does the same
as TCP_CORK except that we don't have to remove TCP_NODELAY before
and we don't need any syscall to set/remove it. This can save up
to 4 syscalls around a send() (two for setting it, two for removing
it), and it's much cleaner since it is not persistent. So make use
of it instead.
diff --git a/include/types/fd.h b/include/types/fd.h
index a50d076..3ab89fe 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -63,8 +63,7 @@
  */
 #define FD_FL_TCP               0x0001       /* socket is TCP */
 #define FD_FL_TCP_NODELAY       0x0002
-#define FD_FL_TCP_CORK          0x0004
-#define FD_FL_TCP_NOLING        0x0008       /* lingering disabled */
+#define FD_FL_TCP_NOLING        0x0004       /* lingering disabled */
 
 /* info about one given fd */
 struct fdtab {