Noissue - Add conversion function from 'BSTR' to 'std::wstring'

Noissue - Add conversion function from 'BSTR' to 'std::wstring'

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Extracted from the following review:
    https://codereview.adblockplus.org/29331055/

The function defined here is the only dependency of 
another review which depended upon the one above:
    https://codereview.adblockplus.org/29332057/

Extracted to avoid dependency delays.

[Eric, 2015-12-09 13:13:49]

In order to avoid delays about whether some code is too beautiful to live, I've
extracted one function definition from a dependent review in order to allow
another to proceed without delay.

[sergei, 2015-12-09 13:20:09]

LGTM

[Oleksandr, 2015-12-14 00:56:23]

LGTM