Be more highlight friendly

Summary:
Some editors (nano, Atom) struggle with a single double quote
enclosed in a {} block.

This change escapes more traditionally the double quote to avoid them
to correctly highlight the source code in Core.

PEP 20

"Although practicality beats purity."

Test Plan: xmlescape {"a"} returns "a".

Reviewers: dereckson

Reviewed By: dereckson

Subscribers: xcombelle

Differential Revision: https://devcentral.nasqueron.org/D1324