bnc#829017 fix issue with negative seeks in win32 shell extension

Change-Id: Ia8072f78ad43281e406377922f50f8de53194f1b

shell/inc/internal/stream_helper.hxx

@@ -31,7 +31,7 @@ public:
     ~BufferStream();
     unsigned long sread (unsigned char *vuf, unsigned long size);
     long stell ();
-    long sseek (unsigned long offset, int origin);
+    long sseek (long offset, int origin);
 private:
     IStream *stream;
 };
@@ -43,7 +43,7 @@ public:
     ~FileStream();
     unsigned long sread (unsigned char *buf, unsigned long size);
     long stell ();
-    long sseek (unsigned long offset, int origin);
+    long sseek (long offset, int origin);
 private:
     FILE *file;
 };

shell/inc/internal/types.hxx

@@ -78,7 +78,7 @@ public:
     virtual ~StreamInterface() {}
     virtual unsigned long sread (unsigned char* vuf, unsigned long size) = 0;
     virtual long stell () = 0;
-    virtual long sseek (unsigned long offset, int origin) = 0;
+    virtual long sseek (long offset, int origin) = 0;
 };
 
 #endif

shell/source/win32/shlxthandler/ooofilt/stream_helper.cxx

@@ -74,7 +74,7 @@ long BufferStream::stell ()
         return -1;
 }
 
-long BufferStream::sseek (unsigned long offset, int origin)
+long BufferStream::sseek (long offset, int origin)
 {
     HRESULT hr;
     LARGE_INTEGER Move;
@@ -129,7 +129,7 @@ long FileStream::stell ()
     return -1L;
 }
 
-long FileStream::sseek (unsigned long offset, int origin)
+long FileStream::sseek (long offset, int origin)
 {
     if (file)
         return fseek(file, offset, origin);