Add on_rightclick(pos, node, clicker) callback for nodes
Repeated right clicking when holding the right mouse button
Configure using repeat_rightclick_time in minetest.conf
Switch to fly mode if spacebar is doubleclicked
Can be turned off in the key change GUI or in minetest.conf via doubletab_space
Fixed content_abm aliases

Since commit 5a13c49492 when I'm in a new area of the world that hasn't
yet been generated the debug log gets flooded with the following error:

Map::setNode(): Not allowing to place CONTENT_IGNORE while trying to
replace "default:dirt_with_grass" at (729,1,-219) (block (45,0,-14))

This commit fixes that.
Fix typo doubletab -> doubletap
Implement textarea in formspec, a multiline input field
"or" should be "||". Don't use "or", "and", etc.. It breaks build.