[OpenMP] Parsing and sema support for the from clause

Summary:
The patch contains the parsing and sema support for the `from` clause. 

Patch based on the original post by Kelvin Li.

Reviewers: hfinkel, carlo.bertolli, kkwli0, arpith-jacob, ABataev

Subscribers: caomhin, cfe-commits

Differential Revision: http://reviews.llvm.org/D18488

llvm-svn: 270882
diff --git a/clang/lib/Basic/OpenMPKinds.cpp b/clang/lib/Basic/OpenMPKinds.cpp
index 4a3423b..5e0e9ba 100644
--- a/clang/lib/Basic/OpenMPKinds.cpp
+++ b/clang/lib/Basic/OpenMPKinds.cpp
@@ -163,6 +163,7 @@
   case OMPC_hint:
   case OMPC_uniform:
   case OMPC_to:
+  case OMPC_from:
     break;
   }
   llvm_unreachable("Invalid OpenMP simple clause kind");
@@ -299,6 +300,7 @@
   case OMPC_hint:
   case OMPC_uniform:
   case OMPC_to:
+  case OMPC_from:
     break;
   }
   llvm_unreachable("Invalid OpenMP simple clause kind");