configure: check for compound literals
Follow-up to #43826. Check to make sure that compound literals are supported by the C compiler.
Attached patch adds new, separate, C99 compound literals check. It would have also been possible to extend the C99 initializers to include part also for this, with less code duplication between the two very similar checks.
Follow-up to #43826. Check to make sure that compound literals are supported by the C compiler.