squelch compiler warnings about not using bytes_read/bytes_written

main/BMP.cc

@@ -41,6 +41,7 @@ bool BMP::open(const char * fileName)
 		// read image information
 		bytes_read = fread(&m_info, sizeof(m_info), 1, m_fp);	
     }
+    (void)bytes_read;
     return (m_fp != NULL);
 }
 
@@ -91,6 +92,7 @@ bool BMP::create(const char * fileName, int width, int height,
             data_ptr -= 3 * width;
         }
     }
+    (void)bytes_written;
     return (m_fp != NULL);
 }
 
@@ -117,6 +119,7 @@ void BMP::read(unsigned char * buf)
             data_ptr -= row_data_bytes;
         }
     }
+    (void)bytes_read;
 }
 
 void BMP::close()