dwebp: warn when decoding animated webp's
dwebp: warn when decoding animated webp's

the decode will fail; provide a bit more background info

Change-Id: Iecccb09cf0fa9f8c1c3e87636a55e1f251dee023

jiehu5114/libwebp,kleopatra999/webm.libwebp,ttyangf/libwebp,zofuthan/libwebp,webmproject/libwebp,abwiz0086/webm.libwebp,ya7lelkom/libwebp,comoyo/gonzo-libwebp,Aexyn/libwebp,ericmckean/webm.libwebp,jacklicn/libwebp,imazen/libwebp,matanbs/webm.libwebp,comoyo/gonzo-libwebp,zofuthan/libwebp,zofuthan/libwebp,Acidburn0zzz/webm.libwebp,ya7lelkom/libwebp,comoyo/gonzo-libwebp,jacklicn/libwebp,Suvarna1488/webm.libwebp,Acidburn0zzz/webm.libwebp,Maria1099/webm.libwebp,ya7lelkom/libwebp,kim42083/webm.libwebp,Distrotech/libwebp,zofuthan/libwebp,cysp/libwebp,gshORTON/webm.libwebp,imazen/libwebp,kim42083/webm.libwebp,ya7lelkom/libwebp,abwiz0086/webm.libwebp,yohunl/libwebp,altogother/webm.libwebp,Maria1099/webm.libwebp,kim42083/webm.libwebp,ericmckean/webm.libwebp,Tekserve/libwebp,yohunl/libwebp,rxl194/libwebp,ttyangf/libwebp,Maria1099/webm.libwebp,Tekserve/libwebp,cysp/libwebp,Suvarna1488/webm.libwebp,kleopatra999/webm.libwebp,kim42083/webm.libwebp,Maria1099/webm.libwebp,kleopatra999/webm.libwebp,PKRoma/libwebp,Acidburn0zzz/webm.libwebp,Suvarna1488/webm.libwebp,jiehu5114/libwebp,jacklicn/libwebp,abwiz0086/webm.libwebp,iniwf/webm.libwebp,rxl194/libwebp,appunite/libwebp,kleopatra999/webm.libwebp,Acidburn0zzz/webm.libwebp,Tekserve/libwebp,kalli123/webm.libwebp,altogother/webm.libwebp,yohunl/libwebp,PKRoma/libwebp,ya7lelkom/libwebp,Distrotech/libwebp,reimaginemedia/webm.libwebp,jiehu5114/libwebp,redengineer/libwebp,yohunl/libwebp,keane83/BLE_IM,ttyangf/libwebp,reimaginemedia/webm.libwebp,rxl194/libwebp,redengineer/libwebp,appunite/libwebp,Suvarna1488/webm.libwebp,appunite/libwebp,kalli123/webm.libwebp,redengineer/libwebp,Aexyn/libwebp,ttyangf/libwebp,reimaginemedia/webm.libwebp,redengineer/libwebp,altogother/webm.libwebp,kalli123/webm.libwebp,Tekserve/libwebp,Suvarna1488/webm.libwebp,imazen/libwebp,Aexyn/libwebp,cysp/libwebp,webmproject/libwebp,Aexyn/libwebp,comoyo/gonzo-libwebp,ericmckean/webm.libwebp,Maria1099/webm.libwebp,matanbs/webm.libwebp,PKRoma/libwebp,jiehu5114/libwebp,redengineer/libwebp,imazen/libwebp,matanbs/webm.libwebp,rxl194/libwebp,gshORTON/webm.libwebp,reimaginemedia/webm.libwebp,webmproject/libwebp,ttyangf/libwebp,abwiz0086/webm.libwebp,abwiz0086/webm.libwebp,yohunl/libwebp,zofuthan/libwebp,Distrotech/libwebp,appunite/libwebp,kleopatra999/webm.libwebp,iniwf/webm.libwebp,iniwf/webm.libwebp,matanbs/webm.libwebp,keane83/BLE_IM,keane83/BLE_IM,kalli123/webm.libwebp,appunite/libwebp,appunite/libwebp,webmproject/libwebp,jiehu5114/libwebp,gshORTON/webm.libwebp,kalli123/webm.libwebp,altogother/webm.libwebp,comoyo/gonzo-libwebp,cysp/libwebp,iniwf/webm.libwebp,jacklicn/libwebp,ericmckean/webm.libwebp,ericmckean/webm.libwebp,kim42083/webm.libwebp,PKRoma/libwebp,PKRoma/libwebp,comoyo/gonzo-libwebp,gshORTON/webm.libwebp,jacklicn/libwebp,reimaginemedia/webm.libwebp,keane83/BLE_IM,gshORTON/webm.libwebp,PKRoma/libwebp,webmproject/libwebp,iniwf/webm.libwebp,Acidburn0zzz/webm.libwebp,rxl194/libwebp,matanbs/webm.libwebp,altogother/webm.libwebp,comoyo/gonzo-libwebp,keane83/BLE_IM,imazen/libwebp,Aexyn/libwebp