Makefile.vc: add anim_diff build support.
Makefile.vc: add anim_diff build support.

Change-Id: Ib5efc5cffea2d906640c81348db26ae28d28d3f1

webmproject/libwebp,PKRoma/libwebp,ya7lelkom/libwebp,rxl194/libwebp,zofuthan/libwebp,imazen/libwebp,webmproject/libwebp,imazen/libwebp,yohunl/libwebp,rxl194/libwebp,PKRoma/libwebp,Aexyn/libwebp,Aexyn/libwebp,redengineer/libwebp,redengineer/libwebp,ya7lelkom/libwebp,redengineer/libwebp,webmproject/libwebp,Aexyn/libwebp,Aexyn/libwebp,webmproject/libwebp,imazen/libwebp,ttyangf/libwebp,PKRoma/libwebp,zofuthan/libwebp,Aexyn/libwebp,ttyangf/libwebp,imazen/libwebp,webmproject/libwebp,rxl194/libwebp,rxl194/libwebp,redengineer/libwebp,rxl194/libwebp,zofuthan/libwebp,PKRoma/libwebp,ya7lelkom/libwebp,zofuthan/libwebp,ttyangf/libwebp,PKRoma/libwebp,imazen/libwebp,yohunl/libwebp,zofuthan/libwebp,ttyangf/libwebp,yohunl/libwebp,yohunl/libwebp,redengineer/libwebp,PKRoma/libwebp,yohunl/libwebp,ya7lelkom/libwebp,ya7lelkom/libwebp,ttyangf/libwebp