Update libgifski on Windows

Author: jeroen

src/Makevars.win

@@ -1,4 +1,4 @@
-RWINLIB = ../windows/gifski-0.8.4
+RWINLIB = ../windows/gifski-0.8.6
 PKG_CPPFLAGS= -I$(RWINLIB)/include
 PKG_LIBS= -L$(RWINLIB)/lib${R_ARCH} \
 	-lgifski -lws2_32 -ladvapi32 -luserenv -ldbghelp

tools/winlibs.R

@@ -1,7 +1,7 @@
 # Build against gifski libs compiled with the Rtools
-if(!file.exists("../windows/gifski-0.8.4/include/gifski.h")){
+if(!file.exists("../windows/gifski-0.8.6/include/gifski.h")){
   if(getRversion() < "3.3.0") setInternet2()
-  download.file("https://github.com/rwinlib/gifski/archive/v0.8.4.zip", "lib.zip", quiet = TRUE)
+  download.file("https://github.com/rwinlib/gifski/archive/v0.8.6.zip", "lib.zip", quiet = TRUE)
   dir.create("../windows", showWarnings = FALSE)
   unzip("lib.zip", exdir = "../windows")
   unlink("lib.zip")