Provide http-config option for curl low-speed-limit/time
Provide http-config option for curl low-speed-limit/time

Fixes rust-lang/cargo#5717

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