D compiler need -nogc witch and document of library also need nogc button

[dangbinghoo]

hi there,

I think that D compiler needs -nogc switch to fully disable gc 
for a project, and document of phobos also needs a friendly way 
to list-out all @nogc API.

we already have -betterC, and betterC disabled GC, why we could 
not have a standalone option for doing this?



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binghoo dang