So the type of Elab now gives the expected type that's being elaborated
to, meaning that we can run 'check' in the middle of scripts and use the
result.
A %macro must always be fully applied. Whenever the elaborator
encounters a %macro application (except in a function LHS) it evaluates
the application and sends the result to %runElab. So:
%macro
foo : args -> Elab TT
...
def = foo a b c
is equivalent to
foo : args -> Elab TT
...
def = %runElab foo a b c
If available (sometimes, say a top level expression, it might need
inferring so there'll be no goal available). Also add the ability to log
the current goal, or indeed any term.
Add %runElab and start on scripts, although all they can do so far is
check a term. This does gives us, sort of, "template Idris" (as
demonstrated in test reflection002)
