wiki: D on AVR

[Ernesto Castellotti]

Hi,

I wrote a page in the wiki for basic information on how to use D 
on AVR 8-bit, using LLVM and LDC.

https://wiki.dlang.org/D_on_AVR

With BetterC everything seems to be working fine, now it's time 
to create a framework for using D on microcontrollers!