In deterministic mode, RAND_MAX is not related to the result of
zeek::random_number() (formerly bro_random()), but some logic was
using RAND_MAX as indication of the possible range of values. The
new zeek::max_random() will give the correct upper-bound regardless
of whether deterministic-mode is used.
This unfortunately cuases a ton of flow-down changes because a lot of other
code was depending on that definition existing. This has a fairly large chance
to break builds of external plugins, considering how many internal ones it broke.
Most of these changes are either cmake-related or plugin-related.
Added a new test "plugins/legacy.zeek" to test that legacy Bro plugins
still work.
Also added a symlink bro-path-dev.in because some legacy Bro packages
won't install without it.
