[OPENMP 4.0] Initial support for array sections.

Adds parsing/sema analysis/serialization/deserialization for array sections in OpenMP constructs (introduced in OpenMP 4.0).
Currently it is allowed to use array sections only in OpenMP clauses that accepts list of expressions.
Differential Revision: http://reviews.llvm.org/D10732

llvm-svn: 245937
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 1e777a5..3f40743 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2712,6 +2712,7 @@
   case Expr::LambdaExprClass:
   case Expr::MSPropertyRefExprClass:
   case Expr::TypoExprClass:  // This should no longer exist in the AST by now.
+  case Expr::OMPArraySectionExprClass:
     llvm_unreachable("unexpected statement kind");
 
   // FIXME: invent manglings for all these.