src: don't use locale-sensitive strcasecmp() (v4.x)#7660

bnoordhuis wants to merge 2 commits intonodejs:v4.x-stagingnodejs/node:v4.x-stagingfrom

bnoordhuis:backport-pr6582-v4.xbnoordhuis/io.js:backport-pr6582-v4.xCopy head branch name to clipboard