Tests shouldn't read from stdin.

As far as I can tell, the only reason run-pass/type-use-i1-versus-i8
is trying to do a read is because that code was left over from the
original program the issue was found in.  When that test is run as
part of check-fast, and apparently only in that case, the test blocks
indefinitely, which is bad.
auto merge of #5000 : jld/rust/test-stdin-thing, r=graydon

As far as I can tell, the only reason run-pass/type-use-i1-versus-i8
is trying to do a read is because that code was left over from the
original program the issue was found in.  When that test is run as
part of check-fast, and apparently only in that case, the test blocks
indefinitely, which is bad.