Speeding up importing Phobos files

[KnightMare]

On Saturday, 8 June 2019 at 12:26:56 UTC, KnightMare wrote:
> LDC can store there optimized LLVM-IR code for AST-tree, so 
> compilation time will be: compile user code only, link and 
> write result to FS
template code will be taken from AST still.
(we just cant compile template for all types in universe to 
IR-code. also maybe IR can store some generics. dunno)