[analyzer] Fix missed leak from MSVC specific allocation functions

Add the wide character strdup variants (wcsdup, _wcsdup) and the MSVC
version of alloca (_alloca) and other differently named function used
by the Malloc checker.

A patch by Alexander Riccio!

Differential Revision: http://reviews.llvm.org/D17688

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@262894 91177308-0d34-0410-b5e6-96231b3b80d8