Add initial class for HD44780 LCD devices.
Add NullPin class as alternative to conditional metaprogramming.

NullPin is pin which doesn't exist. All methods are null and will
be dead-code eliminated.
Switch to use NullPin.
Some compilers have putc as macro.
Add standard Arduino pin numbers.
Add defines for avr-gcc headers compatibility.
Add double-include protection.
Avoid using MCU-specific libs.
Add LCD example.
hd44780: Add delays per datasheet.