Fix building for 32-bit architectures. Fix Int overflow.

[Krivoblotsky]

What

Fix possible Int overflow when building for 32-bit architectures by increasing the size to Int64.
See related issue #534

Why

The build is failing and overflow issues are possible

Affected Areas

Timestamp generation in GRPCTimeout.swift

[MrMage]

Thank you!

[saudeoncovr]

@MrMage are we able to get a new 1.0.0-alpha.3 tagged release that includes this and #538? Or even @glbrntt?

Unfortunately our CI is failing to compile due to the Int overflow error.

[MrMage]

@MrMage are we able to get a new 1.0.0-alpha.3 tagged release that includes this and #538? Or even @glbrntt?

Unfortunately our CI is failing to compile due to the Int overflow error.

That might be possible. Until then, could you simply point your Package.swift to the nio branch instead of a specific version?

[glbrntt]

Fine with me if you don't mind cutting it @MrMage :)

[MrMage]

Done: https://github.com/grpc/grpc-swift/releases/tag/1.0.0-alpha.3