Comment out debug printf() in pdf.c

The printf() about the number of links on a page is very useful, but
only for debugging. As other instances of debugging printf() in djvu.c
and pdf.c are commented out, it seemed consistent to do the same with
this one.

pdf.c

@@ -623,7 +623,7 @@ static int getPageLinks(lua_State *L) {
 		lua_rawseti(L, -2, ++link_count);
     }
 
-	printf("## getPageLinks found %d links in document\n", link_count);
+	//printf("## getPageLinks found %d links in document\n", link_count);
 
 	fz_drop_link(page->doc->context, page_links);