#1 batch behaviour of mismatched defs in imported modules

[Tim]

As per 423AC234.1000809@t-online.de, if you've got some
incorrect syntax in an imported module, such as

def pi=4*atan 1;

then you get your deserved "Value mismatch in
definition" error, but execution continues unabated. In
case of such an error, it should probably stop to
facilitate debugging in interactive mode, or abort
completely in batch mode.

[Tim]

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Also this is missing a file:line# so if I weren't aware of
which edits I was testing, it could be *anywhere* in the
source. Eek!

[Albert Graef]

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Fixed (kind of). The interpreter now recovers from such
errors (continuing execution of remaining initialization
code) and gives a proper error message with filename and
line number for each of them. In batch mode the interpreter
then exits with an exit code of 2.

Is that good enough?

Note that there is no way to report such errors in the
debugger, as no rule is executing and hence there's no stack
frame the debugger could be invoked upon. Thus I decided
that in interactive mode it would be more friendly to
continue to the command prompt, instead of bailing out.
After all these are only runtime errors, so when the
interpreter is running interactively, the user should be
given an opportunity to determine what went wrong and fix
things manually.