PDF written highlights: fix boxes, trash cached tiles

TileCacheItem: add created_ts property.
Document: manage a tile_cache_validity_ts and ignore
older cached tiles.
This timestamps is updated when highlights are written
as annotations in, or deleted from, the PDF, so we can
get the most current rendered bitmap from MuPDF and
avoid highlight ghosts on old tiles.
Save this timestamp in doc settings so older cached to
disk tiles will also be ignored across re-openings.
Bump base for: mupdf.lua: update frontend pboxes with
MuPDF adjusted ones.

frontend/document/document.lua

@@ -372,6 +372,18 @@ function Document:postRenderPage()
     return nil
 end
 
+function Document:getTileCacheValidity()
+    return self.tile_cache_validity_ts
+end
+
+function Document:setTileCacheValidity(ts)
+    self.tile_cache_validity_ts = ts
+end
+
+function Document:resetTileCacheValidity()
+    self.tile_cache_validity_ts = os.time()
+end
+
 function Document:getFullPageHash(pageno, zoom, rotation, gamma, render_mode, color)
     return "renderpg|"..self.file.."|"..self.mod_time.."|"..pageno.."|"
                     ..zoom.."|"..rotation.."|"..gamma.."|"..render_mode..(color and "|color" or "")
@@ -386,7 +398,16 @@ function Document:renderPage(pageno, rect, zoom, rotation, gamma, render_mode)
         hash_excerpt = hash.."|"..tostring(rect)
         tile = DocCache:check(hash_excerpt)
     end
-    if tile then return tile end
+    if tile then
+        if self.tile_cache_validity_ts then
+            if tile.created_ts and tile.created_ts >= self.tile_cache_validity_ts then
+                return tile
+            end
+            logger.dbg("discarding stale cached tile")
+        else
+            return tile
+        end
+    end
 
     self:preRenderPage()
 
@@ -411,6 +432,7 @@ function Document:renderPage(pageno, rect, zoom, rotation, gamma, render_mode)
     -- prepare cache item with contained blitbuffer
     tile = TileCacheItem:new{
         persistent = true,
+        created_ts = os.time(),
         excerpt = size,
         pageno = pageno,
         bb = Blitbuffer.new(size.w, size.h, self.render_color and self.color_bb_type or nil)