[clang-tidy] add cert's VariadicFunctionDefCheck as cppcoreguidelines-pro-type-vararg-def

Summary:
Import the cert check for variadic function definitions into
cppcoreguidelines module to check part of
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-type8-avoid-reading-from-varargs-or-passing-vararg-arguments-prefer-variadic-template-parameters-instead

Reviewers: alexfh, sbenza, bkramer, aaron.ballman

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D13785

llvm-svn: 250468