Merge branch 'userspace_fexec' into 'master'

.gitmodules

Cargo.lock

Cargo.toml

Makefile

renamesyms.sh

rust-toolchain

src/crt0/src/lib.rs

src/header/stdlib/mod.rs

src/header/sys_auxv/mod.rs

src/ld_so/linker.rs

src/ld_so/mod.rs

src/ld_so/start.rs

src/lib.rs

src/platform/auxv_defs.rs

src/platform/mod.rs

src/platform/pte.rs

src/platform/redox/clone.rs

src/platform/redox/exec.rs

src/platform/redox/extra.rs

src/platform/redox/mod.rs