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

+ 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
+ Simplified read_line to reduce cyclomatic complexity

+ renamed example files read.lua and read_line.lua
+ moved #define READ_LINE_SIZE to top of file
+ renamed g_linebuf to linebuf, and moved it into read_line as a static variable

examples/lua/read.lua

@@ -0,0 +1,14 @@
+read(1000, 6000) -- initial config
+send("\n")
+msleep(100)
+read(650, 60) -- main menu
+send("S") -- S menu
+msleep(30)
+read(650, 60)
+send("t") -- Parallel Value Table
+read(650, 60)
+while true do
+  msleep(1000)
+  send("t")
+  read(650, 50) -- repeat PVT forever
+end

examples/lua/read_line.lua

@@ -0,0 +1,17 @@
+read(1000, 8000) -- read initial config
+send("\n")
+read(650, 100) -- main menu
+send("S") -- S menu
+n = 1
+while n > 0 do -- while not empty, read more
+  n, str = read_line(25)
+end
+while true do
+  send("t") -- query PV table
+  msleep(880)
+  n = 1
+  while n > 0 do -- while not empty, read more
+    n, str = read_line(60)
+    msleep(60)
+  end
+end