+ Add system timestamps to lua read() and new lua read_line() per global options; prevented warnings

+ Add missing timestamp-format epoch; update send_ to use fsync and tcdrain like normal tty_sync does; rework read_line to save partial line at timeout

examples/lua/pvt.lua

@@ -0,0 +1,16 @@
+send("\n")
+msleep(100)
+-- read buffer with 0.5 sec delay
+read(160, 500)
+send("S")
+msleep(100)
+-- read buffer
+read(160, 500)
+-- query Parallel Value Table
+send("t")
+print(read(300, 500))
+while true do
+  sleep(1)
+  send("t")
+  print(read(300, 500))
+end