Replace static_cast<const A*> with cast<A> throughout MicrosoftMangle.cpp

Hi John,

Can you please review this small patch attached?
I want to get rid of static_cast in MicrosoftMangle so one won't
copy-paste it somewhere else where it is not appropriate.

Thanks,
Timur Iskhodzhanov,
Google Russia

no_static_cast.patch (2.2 KB)

Committed as r162683.

John.