gotd's session.c file has been split in two, so update the sources to accommodate this change.

Now that gotd has the start of helpers, got-notify-email is the first. This is still behind the --enable-gotd flag.

When running 'make dist', include the correct chroot-*.c file.

Rather than hard-code assumptions into gitwrapper and gotd binaries, allow for some values to be overriden at compile time. This should help portability.

Reads (git clone) are working but writes (git push) run into an error

Bring gotd and gitwrapper closer to how libraries are detected.

Include listen.c; make it portable.

This enables gotd -- for now, this is opt-in at compile-time, via: ./configure --enable-gotd