NTL error callback mechanism and possibly extra interfaces

[pcpa]

I asked in the NTL mailing list about adding the sagemath patch to upstream, and also about quoting Victor response in a sagemath trac for more feedback about possibly adding interfaces to wrap other lower level error functions, so, here it is:

Hi Paulo,

Sounds reasonable...but I'm not planning on releasing an update at least for a few months. Also, there are some "low level" error functions (called by the long integer modules, which are written in C)...do you want/need the "call back" functionality there, too?

-- Victor