add an extra #ifdef WEBP_EXPERIMENTAL_FEATURES to avoid 'unused variable' warning
add an extra #ifdef WEBP_EXPERIMENTAL_FEATURES to avoid 'unused variable' warning

Change-Id: I8a42781eab1fad75e13cb85ac3f768d2405726e0

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