Handle the BlitBuffer struct changes

* stride is now a size_t
  On some platforms, that's 64 bits, which means it's no longer
  automatically converted to a Lua number to avoid precision loss.
  Do that ourselves, because lua-serialize doesn't know how to handle an
  uint64_t cdata ;).

frontend/document/tilecacheitem.lua

@@ -15,7 +15,7 @@ end
 function TileCacheItem:dump(filename)
     logger.dbg("dumping tile cache to", filename, self.excerpt)
     return serial.dump(self.size, self.excerpt, self.pageno,
-            self.bb.w, self.bb.h, self.bb.stride, self.bb:getType(),
+            self.bb.w, self.bb.h, tonumber(self.bb.stride), self.bb:getType(),
             Blitbuffer.tostring(self.bb), filename)
 end
 

frontend/ui/widget/imagewidget.lua

@@ -205,7 +205,7 @@ function ImageWidget:_loadfile()
                 -- cache this image
                 logger.dbg("cache", hash)
                 cache = ImageCacheItem:new{ bb = self._bb }
-                cache.size = cache.bb.stride * cache.bb.h
+                cache.size = tonumber(cache.bb.stride) * cache.bb.h
                 ImageCache:insert(hash, cache)
             end
         end

plugins/coverbrowser.koplugin/bookinfomanager.lua

@@ -450,7 +450,7 @@ function BookInfoManager:extractBookInfo(filepath, cover_specs)
                     dbrow.cover_w = cbb_w
                     dbrow.cover_h = cbb_h
                     dbrow.cover_btype = cover_bb:getType()
-                    dbrow.cover_bpitch = cover_bb.stride
+                    dbrow.cover_bpitch = tonumber(cover_bb.stride)
                     local cover_data = Blitbuffer.tostring(cover_bb)
                     cover_bb:free() -- free bb before compressing to save memory
                     dbrow.cover_datalen = cover_data:len()