banker's rounding

[John W. Eaton]

On 10-Mar-2008, Jaroslav Hajek wrote:

| somehow I was unable to send the patch properly during the weekend, so
| here it is again (hopefully). I'm surprised I haven't found banker's
| rounding in Matlab (not even finance or stat toolbox) - that's why I
| came up with a new name. In case I've just overlooked it, please
| correct the name.

I applied this patch with a few additional changes:

  * check for trunc in configure
  * define xtrunc in lo-mappers.cc

Maybe we should also have a trunc mapper function?

Thanks,

jwe