Per N3924, mark random_shuffle as deprecated in the synopsis for <algorithm>. Since we don't actually do anything when a call is deprecated, there is no functionality change. Maybe someday, we'll decide to warn when using a deprecated function.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@202672 91177308-0d34-0410-b5e6-96231b3b80d8