This modifies the panic feature to accept a boolean or a string. If true
or not empty, then it will cause the panic. This makes some of the error
code a little less ugly.
It's valuable to check your runtime values and to shut down the entire
engine in case something doesn't match. This patch adds some magic
plumbing to support a "panic" mechanism.
A new "panic" statement gets transparently converted into a panic
function and panic resource. The former errors if the input is not
empty. The latter must be present to consume the value, but doesn't
actually do anything.
