clang-format: Understand __attribute__s preceding parameter lists.

Before:
  ReturnType __attribute__((unused))
      function(int i);

After:
  ReturnType __attribute__((unused))
  function(int i);

This fixes llvm.org/PR18632.

llvm-svn: 200337
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 1a19754..efc563b 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -4394,6 +4394,8 @@
 
 TEST_F(FormatTest, UnderstandsAttributes) {
   verifyFormat("SomeType s __attribute__((unused)) (InitValue);");
+  verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa __attribute__((unused))\n"
+               "aaaaaaaaaaaaaaaaaaaaaaa(int i);");
 }
 
 TEST_F(FormatTest, UnderstandsEllipsis) {