Fix the problem that frame rate becomes slower than the specified value.
Merge pull request #2993 from nistetsurooy/more-precise-fps

Fix the problem that frame rate becomes slower than the specified value.
ofSetFramerate: more explanative variable names and comments + CHANGELOG
fix last ocmmit
linux: more precise timming function through monotonic clock
Merge branch 'master' into feature-emscripten
emscripten: use same timming calls as in linux
emscripten: URL file loader implementation