Remove special functions from JPEG compressor

We can do what we want with the standard methods.

common/rfb/JpegCompressor.cxx

@@ -95,7 +95,7 @@ JpegEmptyOutputBuffer(j_compress_ptr cinfo)
   JpegCompressor *jc = dest->instance;
 
   jc->setptr(jc->getend());
-  jc->overrun(jc->getend() - jc->getstart());
+  jc->check(jc->length());
   dest->pub.next_output_byte = jc->getptr();
   dest->pub.free_in_buffer = jc->avail();
 

common/rfb/JpegCompressor.h

@@ -47,12 +47,6 @@ namespace rfb {
 
     void writeBytes(const void*, int);
 
-    inline rdr::U8* getstart() { return start; }
-
-    inline virtual void overrun(int needed) {
-      return MemOutStream::overrun(needed);
-    }
-
   private:
 
     struct jpeg_compress_struct *cinfo;