configure: check for stdatomic.h

Since this is a C11 feature, it requires -std=c11.

Not actually used for anything yet, that will be added in the following
commits.

This merges libav commit 13f5d2bf75.

Signed-off-by: Wan-Teh Chang <wtc@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Anton Khirnov 2016-11-23 21:54:53 -08:00 committed by Michael Niedermayer
parent 4719e563a4
commit 6a4e24280d