Try to use Projectile to find files in *compilation* buffer if possible.

If not, fallback to the original function.

* projectile.el (projectile-compilation-find-file): Use projectile to find
files in *compilation* buffer if possible.

(projectile-mode): Add the previous function around `compilation-find-file'.

Add/Remove the advice around `compilation-find-file' when the mode is on/off.
Still, there's the problem that looping through the files in a bigger project will be pretty slow, so we should definitely check whether `filename` is absolute or relative to `default-directory` before doing the loop.