Make small-caps work correctly with tr locale

Source/wtf/text/StringImpl.h

Index: Source/wtf/text/StringImpl.h
diff --git a/Source/wtf/text/StringImpl.h b/Source/wtf/text/StringImpl.h
index 32c83bfd88c89bcae2505a54a3e327fa7c5c6851..e7171ea3943a2b027c27420b4e81aef15d02f71d 100644
--- a/Source/wtf/text/StringImpl.h
+++ b/Source/wtf/text/StringImpl.h
@@ -756,6 +756,8 @@ inline PassRefPtr<StringImpl> StringImpl::isolatedCopy() const
     return create(characters16(), m_length);
 }
 
+WTF_EXPORT UChar32 toUpper(UChar32, const AtomicString& localeIdentifier);

[tkent, 2015/05/28 00:38:26]

This function needs a documentation.

StringImpl.{h,cpp} shouldn't have this function, which is unrelated to
StringImpl.

I'm not sure where is the best place.  A candidate is wtf/unicode/.  But adding
AtomicString dependency to wtf/unicode/ is also weird.

[rwlbuis, 2015/05/28 23:03:08]

Unfortunately I didn't find a place. It is especially hard because:
1. it should be inline
2. needs AtomicString

[tkent, 2015/05/29 05:49:50]

Let's put it here, and add TODO(rub.buis) about finding the best location, and
add a document of this functions.

+
 struct StringHash;
 
 // StringHash is the default hash for StringImpl* and RefPtr<StringImpl>