allow ASSERT_ALWAYS_ABORT for debug builds on windows to be true or false

[Stephan Bergmann]

On 10/13/2014 10:07 PM, nicholas ferguson wrote:
> Suggest adding
>
> --enable-assert-dbg-never-abort     prevent assert() aborts in debug mode.

I see no good reason for that.  (If your are so desperate that you need 
that for whatever reason, you should be able to add an ad-hoc patch 
locally, without a need for a permanent switch.)

Stephan