net-timestamp: expand documentation

Expand Documentation/networking/timestamping.txt with new
interfaces and bytestream timestamping. Also minor
cleanup of the other text.

Import txtimestamp.c test of the new features.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/timestamping/Makefile

+# To compile, from the source root
+#
+#    make headers_install
+#    make M=documentation
+
 # kbuild trick to avoid linker error. Can be omitted if a module is built.
 obj- := dummy.o
 
 # List of programs to build
-hostprogs-y := timestamping hwtstamp_config
+hostprogs-y := timestamping txtimestamp hwtstamp_config
 
 # Tell kbuild to always build the programs
 always := $(hostprogs-y)
 
 HOSTCFLAGS_timestamping.o += -I$(objtree)/usr/include
+HOSTCFLAGS_txtimestamp.o += -I$(objtree)/usr/include
 HOSTCFLAGS_hwtstamp_config.o += -I$(objtree)/usr/include
 
 clean:
-	rm -f timestamping hwtstamp_config
+	rm -f timestamping txtimestamp hwtstamp_config