I haven't been able to receive xhc interrupt anyway.

Fix warnings

See merge request !114

Update README's debugging instructions

See merge request redox-os/kernel!113

Fix deadlock in sys: scheme

See merge request !112

This patch fixes a deadlock in the sys: scheme that is triggered
when the iostat resource() is called in the same scope where the RwLock
protecting the scheme's handles is write-locked.

implement remainder for nanosleep

See merge request !110

Final few ptrace changes

See merge request redox-os/kernel!109

I believe this could cause a deadlock if a blocking I/O operation was
interrupted by a signal or otherwise, and decided to exit and close
all files. It's unlikely to happen, but it can happen nontheless. This
removes the mutex, but it's difficult to keep the code tidy. Hopefully
this is good enough.

This will let you stop at process exit and inspect it right before the
process dies.