Change the calling convention for `TimestampProvider` to be `{.nimcall.}`. By
default they are considered `{.closure.}` which implies they use GC'ed memory.
TimestampProvider* = proc (): Timestamp {.nimcall.}
- How to define a global proc pointer/value, used by threads? monster
- Re: How to define a global proc pointer/value, used by thread... boia01
