Makes libs.arc load all *.arc files placed in the load/ directory. Vanilla arc
only preloads a hardcoded list of files. With this hack, instead of adding to
that list when you need a new file autoloaded, or adding code to an existing
file that doesn't obviously belong there, you can just put your code in a file
in load/. Autoloaded files are loaded with 'require rather than vanilla 'load,
which allows them to use 'require to ensure load-ordering.

Please read load/README before adding files to the load/ directory. In
particular, load/ is _not_ the correct place to put arc libraries.