Fixes indent in linkage specification blocks.

We now indent:
extern "C" {
int a;
}

without additional indent inside the extern "C" block.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173045 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/UnwrappedLineParser.cpp b/lib/Format/UnwrappedLineParser.cpp
index 7f9e97e..f1d08a6 100644
--- a/lib/Format/UnwrappedLineParser.cpp
+++ b/lib/Format/UnwrappedLineParser.cpp
@@ -311,6 +311,18 @@
   case tok::kw_return:
     parseReturn();
     return;
+  case tok::kw_extern:
+    nextToken();
+    if (FormatTok.Tok.is(tok::string_literal)) {
+      nextToken();
+      if (FormatTok.Tok.is(tok::l_brace)) {
+        parseBlock(0);
+        addUnwrappedLine();
+        return;
+      }
+    }
+    // In all other cases, parse the declaration.
+    break;
   default:
     break;
   }