Prefer void for unused parameters, rather than assigning an argument to
itself as a) unintelligent compilers won't optimize it out, b) it can't
be used for const parameters, c) it will cause compilation warnings for
clang with -Wself-assign and d) is inconsistent with other areas of the
curl source code.
This now provides a weak random function since PolarSSL doesn't have a
quick and easy way to provide a good one. It does however provide the
framework to make one so it _can_ and _should_ be done...
