Egel interpreter from "https://github.com/egel-lang/egel/" by Marco Devillers.

Instructions to rebuild the executable and compiled libraries from a newer version of egel.

Get sources from github:
`fetch /hackenv/tmp/egel.zip https://github.com/egel-lang/egel/archive
(As of this writing, I used git commit a518d99f704f07f90f507eb59ef904b40dd785dd , but I'll forget to update this readme when I install a newer one.)
Unpack sources:
``` set -e; cd /hackenv/tmp; rm -r egel-master
``` set -e; cd /hackenv/tmp; unzip egel.zip
Build the interpreter. You'll have to rerun this a few time because it's too slow to build for HackEso's timeout, and check for unlucky timeouts while the compiler is writing its output.
``` set -ex; cd /hackenv/tmp/egel-master; make -C src LIBS="-ldl -lpthread -licuio -licui18n -licuuc -licudata" &>> buildlog
Build the compiled libraries.
``` set -ex; cd /hackenv/tmp/egel-master; (for m in io fs random regex; do make -C lib/$m LIBS="-ldl -lpthread -licuio -licui18n -licuuc -licudata"; done) &>> buildlog
Copy the files
``` set -xe; cd /hackenv/tmp/egel-master; cp -v src/egel lib/*.ego /hackenv/interps/egel/
The prelude is currently a custom one for HackEso.  Check if the prelude distributed with egel changed and merge.  In the long term, we should merge changes back from HackEso to egel, or at least a fork.

There should be a wrapper that invokes this, but I haven't yet written one.  Example command that works.
``` set -e; cd egel-scripts; >a0.eg echo $'import "/hackenv/tmp/egel-master/include/prelude-hackeso.eg"\nusing System\nusing Math\nusing String\nusing IO\ndef main = ''[F->F F tuple 2 777][F B L U->[false->B|true->F F([T->T T 2][T C->[true->B|false->[false->B L|true->T T(C+1)](C*C<=L)](0==L%C)])(L+1)U](L<U)]'; /hackenv/interps/egel/egel a0.eg