chm compiler can't deal with hex escaping

[ghost]

Problem

If hex escaping (e.g. ') appears in .hhc/.hhk files, chm compiler will simply ignore it.

Sadly, Python 3's html.escape(s, quote=True) function generates a hex escaping ' for single quote '.

This leading to a compiling issue for Python chm document, please see: https://bugs.python.org/issue35482

Suggestion

htmlhelp builder uses html.escape() twice [1] [2] for .hhc/.hhk files, we can make a wrapper function for html.escape() that convert hex escaping to decimal escaping, e.g. ' -> '

Environment info

• OS: Win
• Python version: any
• Sphinx version: 1.8.2 / 2.0
• Microsoft HTML Help Compiler: 4.74.8702