Reviewed by Maciej.

        - support for WebKit fix for http://bugzilla.opendarwin.org/show_bug.cgi?id=5187
          UTF-8 in long text files breaks at some point

        No layout test added: only affects plain text view and requires loading the
        file in multiple chunks.

        * WebCore.exp: Added WebCoreTextDecoder.
        * kwq/WebCoreTextDecoder.h: Added.
        * kwq/WebCoreTextDecoder.mm: Added.
        * WebCore.xcodeproj/project.pbxproj: Added files, made header private (SPI).

WebKit:

        Reviewed by Maciej.

        - fixed http://bugzilla.opendarwin.org/show_bug.cgi?id=5187
          UTF-8 in long text files breaks at some point

        * WebView.subproj/WebTextRepresentation.m:
        (-[WebTextRepresentation finishedLoadingWithDataSource:]):
        Call flushReceivedData on the WebTextView so it can decode any final bytes.

        * WebView.subproj/WebTextView.h: Added WebCoreTextDecoder field and flushReceivedData method.
        * WebView.subproj/WebTextView.m:
        (-[WebTextView dealloc]): Release WebCoreTextDecoder.
        (-[WebTextView appendReceivedData:fromDataSource:]): Create a WebCoreTextDecoder to decode
        the text; use the textEncodingName from the data source. Use it to decode instead of the
        data source's stringWithData.
        (-[WebTextView flushReceivedData]): Call flush on the decoder and append any last bytes to
        the text view.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@10797 268f45cc-cd09-0410-ab3c-d52691b4dbfc