Remove converting to negative fd

[tak1n]

Opening a PR for it because I'm not entirely sure if it should be removed.
Removing it means following behaviour:

Another way to merge multiple file descriptors is [:child, fd]. [:child, fd] means the file descriptor in the child process. This is different from fd. For example, :err=>:out means redirecting child stderr to parent stdout. But :err=>[:child, :out] means redirecting child stderr to child stdout. They differ if stdout is redirected in the child process as follows.

# stdout and stderr is redirected to log file.
# The file "log" is opened just once.
pid = spawn(command, :out=>["log", "w"], :err=>[:child, :out])

[tak1n]

Note:
Travis still doesn't recognize our 2.2 branch.
We should as soon as possible open a pr from 2.2 to master to get 2.2 specs run on travis.

[chuckremes]

You should create a spec that shows the failure in Process.spawn. It should go somewhere near here:
https://github.com/rubinius/rubinius/blob/2.2/spec/ruby/shared/process/spawn.rb#L335

Then make your code change and verify the behavior is correct. I don't think this PR will be merged without a spec.

[tak1n]

Thx for reviewing accidentally forgot to commit it.

[chuckremes]

Looks good to me. Let's leave it for a few days to see if @yorickpeterse or @brixen have comments before merging it.

[yorickpeterse]

I would use regular English for this instead, so if :err is [:child, :out], but that's a minor detail.

[yorickpeterse]

Regarding Travis, I can't seem to figure out why it's not building the 2.2 branch. Does running ./bin/mspec ci pass all specs?

[tak1n]

All the specs which were marked as failing (IO popen) and my Process.spawn spec pass.
There are these nil/true/false specs failing, but they were already failing.

[yorickpeterse]

👍 Thanks