GC and realtime threads.

[Frank Benoit]

> You can control the GC via the 'std.gc' import, which exposes the
> 'std.gc.disable()' and 'std.gc.enable()' functions for turning automatic
> collection off/on, and the 'std.gc.fullCollect()' function for manually
> initiating a collection run.
> 

disable and enable is not implemented. See dmd/src/phobos/internal/gc/gcx.d
Search for the use of the 'disabled' variable.