win: don't use inline keyword in thread.c
win: don't use inline keyword in thread.c

The reported bug is arguably a compiler bug - a non-static inline
function should be inlined inside the compilation unit but still
have external linkage - but the abundant use of 'inline' isn't
really necessary in the first place.  Remove it.

Fixes: https://github.com/libuv/libuv/issues/191
PR-URL: https://github.com/libuv/libuv/pull/194
Reviewed-By: Bert Belder <9f2ff180696da386c1be31b4507155616db25dc6@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <8a7991f6950ea189abf159d6ec98d2fcc13dc5f6@gmail.com>

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