Some DWARFv5 proposal prototypes (atomic_type, aligned_type)

[Mark Wielaard <mjw@redhat.com>]

Hi,

The following two patches are based on the earlier "dwarf2out.c: Pass
one cv_quals argument" and "Emit DW_tag_restrict_type" patches I posted
earlier. Since there currently is not even an early draft yet for DWARFv5,
just a collection of proposals that might or might not be adopted these
patches are not meant to be integrated just yet. But I would like to get
feedback on the code and whether the new debug information is useful.

I have corresponding patches for gdb so that the new guality.exp tests
PASS (without those they will report UNSUPPORTED). The tests only deal
with C code. It would be interesting if people could provide corresponding
tests for other languages that have atomics and/or user aligned types to
see if it works generically or needs some extra language support.

We could try to make them into GNU extensions if people find them useful,
but because they are type qualifier tags, not simple attributes, it would
need some extra coordination with other DWARF consumers to make sure they
are recognized.

Thanks,

Mark