a more radical attempt at ignoring nil y's

Dependencies

• [2] FM7UDV2G no, bring back that defense
• [3] RT6EV6OP delegate update events to drawings
• [4] AVTNUQYR basic test-enabled framework
• [5] BXJMGTV2 hoist couple of variables out
• [6] PJEQCTBL add state arg to Drawing.update
• [7] EHSUSZMK more idiomatic variable names
• [8] JFFUF5AL override mouse state lookups in tests
• [9] LF7BWEG4 group all editor globals
• [10] 7SFHSB47 rename
• [11] 3QNOKBFM beginnings of a test harness
• [12] WLWNS6FB a bug I've never run into
• [13] DRFE3B3Z mouse buttons are integers, not strings
• [*] BLWAYPKV extract a module

Change contents

• edit in drawing.lua at line 244
  [3.254]→[2.17:124](∅→∅)
  − if drawing.y == nil then

  − -- something invalidated all the y's; just wait for a draw

  − return

  − end
• edit in app.lua at line 37
  [3.499]→[3.499:550](∅→∅)
  −

  − if love.timer then dt = love.timer.step() end
• replacement in app.lua at line 38
  [3.551]→[3.2427:2510](∅→∅)
  − if App.update then App.update(dt) end -- will pass 0 if love.timer is disabled
  [3.551]

  [3.636]
  + -- perform draw before update to give it a chance to mutate state
• edit in app.lua at line 48
  [3.863]

  [3.863]
  +

  + if love.timer then dt = love.timer.step() end

  +

  + if App.update then App.update(dt) end -- will pass 0 if love.timer is disabled