Fix int64_t_t typo in README code example

Fixes a typo where the first type was written as int64_t_t with suffixing _t twice and the second type misses suffix at all.
Merge pull request #3 from sochka/patch-1

Fix int64_t_t typo in README code example
Missing headers for sysctl stuff on OSX
For those using YCM
Better include path for YCM users
sysinfo conditional compilation fixes for OSX
Move linux-only variable into linux/cygwin block
Fix shutting down FastClock's thread on OSX.
[#4] A few minor changes.
[#4] Cleaned up FastClock background thread.
Remove old NOTEs