Auto merge of #4141 - Keruspe:master, r=alexcrichton
Auto merge of #4141 - Keruspe:master, r=alexcrichton

update git2

Fixes build with libressl

nipunn1313/cargo,eminence/cargo,tsurai/cargo,vojtechkral/cargo,tshepang/cargo,nipunn1313/cargo,durka/cargo,eminence/cargo,rustyhorde/cargo,nipunn1313/cargo,tshepang/cargo,achanda/cargo,tsurai/cargo,achanda/cargo,nipunn1313/cargo,rustyhorde/cargo,achanda/cargo,rust-lang/cargo,rustyhorde/cargo,tshepang/cargo,eminence/cargo,tsurai/cargo,durka/cargo,achanda/cargo,rust-lang/cargo,vojtechkral/cargo,tshepang/cargo,tsurai/cargo,eminence/cargo,durka/cargo,rust-lang/cargo,rust-lang/cargo,rustyhorde/cargo,vojtechkral/cargo,durka/cargo,vojtechkral/cargo,tsurai/cargo