avr_timer: refactor avr_timer_write and avr_timer_reconfigure

avr_timer_reconfigure: calculations moved back in call chain to
 avr_timer_write.

avr_timer_configure: use data processed in avr_timer_write.

avr_timer_init: changed to fully trap writes going to as2,
 clock select bits and waveform generation mode bits.

	modified:   ../../simavr/sim/avr_timer.c
	modified:   ../../simavr/sim/avr_timer.h

avr_timer: remove as2 timer check.

	modified:   avr_timer.c
parts: Added SSD1306 OLED driver virtual part
examples: Added SSD1306 example board

atmega32_ssd1306.c 	Example avr firmware
ssd1306.*		SSD1306 avr driver
images.*		simavr logo used in example firmware
ssd1306demo.c		simavr demo for ssd1306 part
Merge pull request #77 from dougszumski/ssd1306_demo

New part & example for a SSD1306 OLED driver
Merge pull request #57 from bsekisser/avr-timer-as2-cs-mode

avr_timer: refactor avr_timer_write and avr_timer_reconfigure