dmd.error: expose ErrorSink to C++ compiler interface

[ibuclaw]

So that gdc/ldc can override the ErrorSinkCompiler class to send errors to their backend diagnostics engine.

e.g:

class ErrorSinkGccCompiler : public ErrorSinkCompiler
{
public:
  static ErrorSinkGccCompiler *create();
  void verror(Loc, const char *, va_list) override final;
  void verrorSupplemental(Loc, const char *, va_list) override final;
  void vwarning(Loc, const char *, va_list) override final;
  void vwarningSupplemental(Loc, const char *, va_list) override final;
  void vdeprecation(Loc, const char *, va_list) override final;
  void vmessage(Loc, const char *, va_list) override final;
  void vdeprecationSupplemental(Loc, const char *, va_list) override final;
};

///

global.errorSink = ErrorSinkGccCompiler::create();

[ibuclaw]

@dkorpel the cpp layout checker can't handle overload sets, but it's not a big deal if they're missing here. :-(

[ibuclaw]

:shakes-head: