d: Don't generate code that throws exceptions when compiling with `-fno-exceptions'

d: Don't generate code that throws exceptions when compiling with `-fno-exceptions'

The version flags for RTMI, RTTI, and exceptions was unconditionally
predefined.  These are now only predefined if the feature flag is
enabled.  It was noticed that there was no `-fexceptions' definition
inside d/lang.opt, so the detection of the exceptions option flag was
only partially working.  Once that was fixed, a few places in the
front-end implementation were found to fall fowl of `nothrow' rules,
these have been fixed upstream and backported here as well.

Reviewed-on: https://github.com/dlang/dmd/pull/15357
	     https://github.com/dlang/dmd/pull/15360

	PR d/110471

gcc/d/ChangeLog:

	* d-builtins.cc (d_init_versions): Predefine D_ModuleInfo,
	D_Exceptions, and D_TypeInfo only if feature is enabled.
	* lang.opt: Add -fexceptions.

gcc/testsuite/ChangeLog:

	* gdc.dg/pr110471a.d: New test.
	* gdc.dg/pr110471b.d: New test.
	* gdc.dg/pr110471c.d: New test.