Adding c++11 support to USE_LANGUAGES

[Jonathan Perkin <jperkin%joyent.com@localhost>]

* On 2017-04-28 at 11:05 BST, Jonathan Perkin wrote:

> * On 2017-04-24 at 13:50 BST, Joerg Sonnenberger wrote:
> 
> > On Mon, Apr 24, 2017 at 02:07:17PM +0200, Edgar Fuß wrote:
> > > Is C++n a superset of C++m for n>m?
> > 
> > Mostly. There are a couple of things that explicitly create problems for
> > m == 2003 and there is the problem of at least one semantic change that
> > can potentially result in miscompiled code (destructors are tagged as
> > not throwing by default in 2011). For m>=2011 it should be transparent.
> 
> In that case what about something like this:
> 
>   https://github.com/joyent/pkgsrc/commit/e33dc10357d54315a5152ccd9895dde5e1d0f256
> 
> tl;dr: introduce CXX_REQD as a similar mechanism to GCC_REQD, packages
> append to it what they need, then we distil it to the most recent
> version and use that for the build.

Joerg suggested rolling this into USE_LANGUAGES instead.  I've done
that here and kicked off a bulk build:

  https://github.com/joyent/pkgsrc/commit/f5841e6549988e345b4a3c5aad7f11d7906f1ea6

One of the issues I've realised is that neither this nor the CXX_REQD
patch will work in bl3 files if compiler.mk has already been read.

I'm not sure there's a great solution for that, so at least
integrating this into USE_LANGUAGES should get us existing pkglint
warnings about setting it after compiler.mk.

Please help testing on NetBSD, especially with problematic packages
like libreoffice, I don't yet have a fast NetBSD VM to test in.

-- 
Jonathan Perkin  -  Joyent, Inc.  -  www.joyent.com