Fail uninstalling toolchain in windows

[danslapman]

Hi! Currently, I have two toolchains installed:
`installed toolchains

stable-i686-pc-windows-gnu
stable-x86_64-pc-windows-gnu (default)

active toolchain

stable-x86_64-pc-windows-gnu (default)
rustc 1.8.0 (db2939409 2016-04-11)`

When i type rustup toolchain uninstall stable-i686-pc-windows-gnu, I get this error:
thread '<main>' panicked at 'internal error: entered unreachable code', src/rustup-cli\rustup_mode.rs:42 note: Run withRUST_BACKTRACE=1for a backtrace.

[peschkaj]

I believe this is a duplicate of #465

[brson]

Closing as dupe. This will be fixed in the next release (not sure when it'll be out). In the meantime, rustup toolchain remove works.