Implement RFC style for match
Implement RFC style for match

Put the opening brace of match arm's body on the next line if the pattern has
guard and consists of multi lines.

graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,SingingTree/rustfmt,aidancully/rust,aidancully/rust,graydon/rust,rust-lang/rustfmt,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,SingingTree/rustfmt,rust-lang/rustfmt,aidancully/rust