Eliminate HAVE(ERRNO_H).

errno.h is available on all platforms that blink supports including Windows. HAVE(ERRNO_H) is used in WebKit to support WinCE which is not a supported platform for blink.

In DateMath.cpp errno is not used, so no need to include errno.h.

Review URL: https://chromiumcodereview.appspot.com/22084002

git-svn-id: svn://svn.chromium.org/blink/trunk@155493 bbb929c8-8fbe-4397-9dbb-9b2b20218538