Your Makefile outputs "libasui-power.so" while the desktop file references "libasui_power.so". I only noticed this one thanks to the following message produced by hildon-desktop:
( - sorry about this, if it came off as rude; the smiley was only there because I had tried many other things [I thought the code, although looking correct, was at fault somehow] and didn't realise it was the name of the file)