Create the m4 directory, and also place .gitignore in there for libtool.
Create the m4 directory, and also place .gitignore in there for libtool.

patch by Jan Engelhardt (jengelh at medozas dot de)

Fixes the error:
aclocal: couldn't open directory "m4": No such file or directory
autoreconf: aclocal failed with exit status: 1

Change-Id: I1c1cd2c3d96f0d7d25616ec084dfc9bf9077fd4f

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