c++: Handle RAW_DATA_CST in modules.cc [PR119076]

c++: Handle RAW_DATA_CST in modules.cc [PR119076]

The following testcases (one with #embed, one with large initializer
turned into RAW_DATA_CST) show that I forgot to handle RAW_DATA_CST in
module streaming.

Similar to the PCH case we need to stream out RAW_DATA_CST with NULL
RAW_DATA_OWNER (i.e. a tree which has data owned by libcpp buffer) so
that it will be streamed back in as STRING_CST which owns the data,
but because the data can be really large (hopefully not so much for
header modules though), without actually trying to build a STRING_CST
on the module writing side because that would mean another large
allocation and copying of the large data.
RAW_DATA_CST with RAW_DATA_OWNER then needs to be streamed out and in
by streaming the owner and offset from owner's data and length.

2025-03-12  Jakub Jelinek  <jakub@redhat.com>

	PR c++/119076
	* module.cc (trees_out::start): Handle RAW_DATA_CST.
	(trees_in::start): Likewise.
	(trees_out::core_vals): Likewise.
	(trees_in::core_vals): Likewise.

	* g++.dg/modules/pr119076-1_a.H: New test.
	* g++.dg/modules/pr119076-1_b.C: New test.
	* g++.dg/modules/pr119076-2_a.H: New test.
	* g++.dg/modules/pr119076-2_b.C: New test.