Features: Reorder the order of GNU dialect feature tests

This doesn't make a difference, but the consistency with other files
is easier to reason about.
Features: Use the correct dialect flag when recording features.

Avoid using -std=c++1y for compilers which support -std=c++14, for
example.
Features: Run GNU feature tests with std=c++14 when available.
Merge topic 'compile-features-refactor' into next

58dcfe0f Features: Run GNU feature tests with std=c++14 when available.
d94e19a4 Features: Use the correct dialect flag when recording features.
a68cdd9f Features: Reorder the order of GNU dialect feature tests
Features: Reorder the GNU C dialect feature tests

This doesn't make a difference, but the consistency with other files
is easier to reason about.
Features: Use the correct dialect flag when recording features.

Avoid using -std=c++1y for compilers which support -std=c++14, for
example.
Features: Run GNU feature tests with std=c++14 when available.
Merge topic 'compile-features-refactor' into next

32b91b9e Features: Run GNU feature tests with std=c++14 when available.
82c283f9 Features: Use the correct dialect flag when recording features.
b18155b7 Features: Reorder the GNU C dialect feature tests