Simplifying druntime and phobos by getting rid of "shared static this()" blocks

[Andrei Alexandrescu via Digitalmars-d]

https://github.com/dlang/phobos/pull/5421

Looking forward to more in the same vein, please contribute! We have 25 
left in phobos and 12 in druntime. A big one will be making the GC 
lazily initialize itself. -- Andrei