Expand scarecrow behavior to three options

[GSKirox]

Change the free_scarecrow option to scarecrow_behavior with 3 options :

• Vanilla
• Fast : you don't need to play the song to summon Pierre, just to pull an Ocarina, but you still need to set a song to child and adult Bonooru.
  This is logically identical to Vanilla.
• Free : same behavior as the old free_scarecow option.

[r0bd0g]

I guess don't forget to make this work together with #2221 when that comes in.