The general rule I'm aiming for is to <> include
system wide / installed paths / generally everything
that's outside the git managed source tree (this means
mruby paths too!), and "" include everything else,
ie. local mkxp headers.
The only current exception are the mri headers, which
all have './' at their front as to not clash with
system wide ruby headers. I'm leaving them be for now
until I can come up with a better general solution.
Releasing a Tilemap atlas into the pool on every map switch
will blow out tons of smaller textures for very little gain,
as atlas textures are already pretty much impossible to
recycle anywhere but in new Tilemaps.