[patch] Default to --enable-libstdcxx-time=auto

[Jonathan Wakely]

On 22 May 2013 11:40, Jonathan Wakely wrote:
> On 22 May 2013 11:30, Paolo Carlini wrote:
>> .. put an abort or something in the dummy implementations, to make sure
>> people don't try to run an executable built with headers which have the
>> clock available linked at run time to a .so which doesn't, really.
>> Suboptimal solution because ideally we would like to fail at build time, but
>> this is the best I have got so far. Be very clear in the docs, anyway.
>
> Based on feedback for <regex> users much prefer to have something
> undefined than to have it defined but non-functional or causing an
> abort.

Could leave the steady_clock::now() symbol "undesignated", like the
__once_call and __once_callable symbols that are only present when
_GLIBCXX_HAVE_TLS is defined?