Make context name a RwLock

src/arch/x86_64/interrupt/syscall.rs

src/context/context.rs

src/context/switch.rs

src/lib.rs

src/scheme/proc.rs

src/scheme/sys/block.rs

src/scheme/sys/context.rs

src/scheme/sys/exe.rs

src/scheme/sys/iostat.rs

src/scheme/sys/syscall.rs

src/syscall/mod.rs

src/syscall/process.rs