lib: fix expensive isNaN call in readable streams
Replace a call to isNaN(n)
with n !== n
. Removes most of the
overhead from the following hotspot:
13.59% iojs perf-603.map [.] LazyCompile:*isNaN
native v8natives.js:67
R=@chrisdickinson, /cc @trevnorris
CI: https://jenkins-iojs.nodesource.com/view/iojs/job/iojs+any-pr+multi/784/