Fix for bug http://llvm.org/PR17427.
Assertion failed: "Computed __func__ length differs from type!"
Reworked PredefinedExpr representation with internal StringLiteral field for function declaration.
Differential Revision: http://reviews.llvm.org/D5365


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@219393 91177308-0d34-0410-b5e6-96231b3b80d8