* Setting: Safe digging and placing
* New setting 'safe_dig_and_place' under Controls
* If set, digging and placing will not auto-repeat
* Releasing buttons unblocks the respective action again
* Useful for inexperienced users in creative mode where default
repeat times may be too short
* Safe placing (right click repetition) does not need a guarding flag
* Added new setting to minetest.conf.example