darwin: reduce memory overhead deleting static member in uv_uptime

[juanarbol]

The uv_uptime function is not the most used function in libuv, storing the uptime selection the whole execution does not make any sense. This patch will make libuv occupy a bit less memory in runtime.

[vtjnash]

This seems slightly less space efficient now, since it must copy the static values to the stack.

[juanarbol]

All the rest of methods are not using a static which, my main concern is not allocation but lifetime. This function called once will result with a copy of the static values for the whole execution, which IMO is not required for a misc function.

[vtjnash]

That does not seem accurate to what static means. The static there means it should not copy the values, but rather use part of the binary to hold the values. Without that, it must generate code to copy those values to the stack.

[juanarbol]

@vtjnash Yeah, right; I'm sorry for all the noise here, I'll proceed to close this one.