Add an option to regex.escape() to not escape spaces

[mrabarnett]

Original report by kovidgoyal (Bitbucket: kovidgoyal, GitHub: kovidgoyal).

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Recently, regex.escape() was changed to also escape spaces, because spaces are significant in VERBOSE patterns. However, escaping spaces is ugly when the escaped string is presented to a user for editing. Could you add another keyword argument to escape() to not escape spaces. So if the caller of escape() knows that the pattern is not going to be used with the VERBOSE flag, they can chosoe not to escape spaces.

[mrabarnett]

Original comment by Matthew Barnett (Bitbucket: mrabarnett, GitHub: mrabarnett).

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Added literal_spaces keyword (default False) to regex.escape function in regex 2017.06.20.