[Sanitizer] Add interceptor for wcsdup

Summary: The wide-string equivalent of strdup. Implementation trivial.

Reviewers: vitalybuka, eugenis

Subscribers: kubamracek, delcypher, llvm-commits, #sanitizers

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D62189

llvm-svn: 361357