[Dlang-internal] Status of C++ .h files in D front end source code

[Walter Bright via Dlang-internal]

Related: https://github.com/dlang/dmd/pull/6334

dmd has converted 100% of the glue code to D. It no longer has any use for the 
.h files in the front end. In other words, the .h files exist only to support 
GDC and LDC.

What are the prospects for reducing the dependence of GDC/LDC on those .h files? 
I figure it is impractical to convert gcc/llvm header files to D in order to 
convert all the glue code to D, but could the glue code be split up into D and 
C++ sources so that the C++ code will no longer need those headers?