Speed up the RGBA->BGRA conversion (FS#1112)

Signed-off-by: Uli Schlachter <psychon@znc.in>
awful.mouse: Follow C API changes

Whoops. This was broken ages ago. Thanks to Elv13 for making me notice.

Signed-off-by: Uli Schlachter <psychon@znc.in>
Add external function for {tag,task,tab}list background image

Signed-off-by: Uli Schlachter <psychon@znc.in>
Add ability to disable tasklist icons and restore ability to set bg_images

Signed-off-by: Uli Schlachter <psychon@znc.in>
Add ability to set background images for empty tag

Signed-off-by: Uli Schlachter <psychon@znc.in>
Allow to disable taglist icons.

This is used if the user want to use a custom drawing method.

Signed-off-by: Uli Schlachter <psychon@znc.in>