[Issue 23535] extend pragma(crt_constructor) with semantics that static constructors have

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23535

--- Comment #1 from Walter Bright <bugzilla at digitalmars.com> ---
crt_destructor should also have C linkage.

crt_constructor should be marked @system because it can modify mutable
variables.

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