[Gm2] tracking trunc

[Gaius Mulley]

hello,

I thought I'd post a message saying that I've brought the master branch
of gm2 up to date and I'm now committing to the master branch on gm2 in
an attempt to track gcc trunc.  cc1gm2 currently builds and then fails
when building libraries (libgm2).  I think this approach should serve
well over time - and should in theory produce timely up to date versions
of gm2 when gcc is released

regards,
Gaius