By default the Makefile installs data into /usr/share (with default prefix
/usr) but the binary is installed into /usr/local/bin (as if the prefix
were /usr/local).
Improve consistency by dropping "local" from the binary path. If the
user wants to install into /usr/local he/she can do PREFIX=/usr/local
Currently the Makefile lets you choose your own PREFIX, but
the installed runanki.system always hardcodes the prefix as /usr.
Fix runanki.system at install time to install into the designated
PREFIX.
