inline some use-once typedefs

Change-Id: I55cc82c8e180cce371c996690608090b1bfdfda4
Reviewed-on: https://gerrit.libreoffice.org/17494
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>

io/source/TextInputStream/TextInputStream.cxx

@@ -50,12 +50,10 @@ namespace io_TextInputStream
 
 // Implementation XTextInputStream
 
-typedef WeakImplHelper2< XTextInputStream2, XServiceInfo > TextInputStreamHelper;
-
 #define INITIAL_UNICODE_BUFFER_CAPACITY     0x100
 #define READ_BYTE_COUNT                     0x100
 
-class OTextInputStream : public TextInputStreamHelper
+class OTextInputStream : public WeakImplHelper2< XTextInputStream2, XServiceInfo >
 {
     Reference< XInputStream > mxStream;