c++: Implement mangling of RAW_DATA_CST [PR118278]

c++: Implement mangling of RAW_DATA_CST [PR118278]

As the following testcases show (mangle80.C only after reversion of the
temporary reversion of C++ large array speedup commit), RAW_DATA_CST can
be seen during mangling of some templates and we ICE because
the mangler doesn't handle it.

The following patch handles it and mangles it the same as a sequence of
INTEGER_CSTs that were used previously instead.
The only slight complication is that if ce->value is the last nonzero
element, we need to skip the zeros at the end of RAW_DATA_CST.

2025-01-03  Jakub Jelinek  <jakub@redhat.com>

	PR c++/118278
	* mangle.cc (write_expression): Handle RAW_DATA_CST.

	* g++.dg/abi/mangle80.C: New test.
	* g++.dg/cpp/embed-19.C: New test.