Add a constant for backspace
board_print -> render_board
delete a dead function
clarify gridfield_place's return value
remove some code duplication in allowed_moves
enable ubsan and asan in debug build
Don't allow players to reshuffle new pieces via undo

Previously, when a player received new pieces they could undo and
re-place their last piece to get a new random set of pieces.

Now we use reentrant rand functions and store their state on struct
Game. When a previous version of Game is restored, so is the previous
PRNG state, thus we get the same set of pieces next time they are
remove extra --debug flag in squell rule
Add 5-long pieces and u shapes

Table needs to be stretched by an extra row and column per piece. it's
tough to tell apart the different lengths so I fill it with period
placeholders instead of spaces
Add hiscores powered by sqlite
Add a note to readme about the hosted game
Add an intro splash screen
explicitly show how to run the game
Add readme with install instructions
add missing time & errno headers
ignore executable
decrease controls width