Add new connection type 'piplate' to the hd44780 driver (by J. Brogdon).

In the documentation replace the list of the connection types for hd44780
driver with the table also used in the configuration options description
(use only a single place to list and link everyting). While there, remove the
assembly code for lcdserializer.

acinclude.m4

@@ -227,6 +227,7 @@ dnl			else
 			fi
 			if test "$x_ac_have_i2c" = yes; then
 				HD44780_DRIVERS="$HD44780_DRIVERS hd44780-hd44780-i2c.o"
+				HD44780_DRIVERS="$HD44780_DRIVERS hd44780-hd44780-piplate.o"
 			fi
 dnl			The hd4470-rpi driver only works on a Raspberry Pi,
 dnl			which is an ARM platform. Require people to compile on