Search: regex doesn't support character classes (e.g. \s, \b, \W, etc.)

[makyen]

When entering a regex into the search page, I expected to be able to use character classes (e.g. \s, \b, \W, etc.). However, when I tried, the results were identical to searching a non-regex with the \ character stripped.

Example:

non-regex	regex
Search for sales	Search for regex sale\s	Results are, erroneously, identical
Search for saleb	Search for regex sale\b	Results are, erroneously, identical

[ArtOfCode-]

Duplicate of #258