ES5.1 section 6 ("Source Text"):
"Throughout the rest of this document, the phrase “code unit” and the
word “character” will be used to refer to a 16-bit unsigned value
used to represent a single 16-bit unit of text."

This changed in ES6 draft section 10.1 ("Source Text"):
"The ECMAScript code is expressed using Unicode, version 5.1 or later.
ECMAScript source text is a sequence of code points. All Unicode code
point values from U+0000 to U+10FFFF, including surrogate code points,
may occur in source text where permitted by the ECMAScript grammars."

This patch is to reflect this spec change.

BUG=v8:3617
LOG=Y
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/640193002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24510 ce2b1a6d-e550-0410-aec6-3dcde31c8c00