Fixes C++ mangling for substituted basic types that are target-specific.
Introduces a new method that currently does nothing, but could in future
make use of flag_abi_version as extern(C++) integration improves in
latter versions of the D front-end.

Reviewed-on: https://github.com/dlang/dmd/pull/9439

gcc/d/ChangeLog:

2019-03-12  Iain Buclaw  <ibuclaw@gdcproject.org>

	* d-lang.cc (d_init_options): Set global.params.cplusplus to C++14.
	* d-target.cc (Target::cppFundamentalType): New method.

From-SVN: r269611