io_splice 4.2.0 - several bugfixes and workarounds

We now limit maximum splice length to (1<<30) to avoid EINVAL
errors on 64-bit hosts.

vmsplice no longer raises Errno::EFAULT optimizations in newer
GCC (not that I've found a good use for vmsplice at all with
Ruby...)

There are several other small cleanups.

Eric Wong (6):
      copy_stream: small cleanup for pipe splicing
      limit maximum splice length to 1 << 30
      avoid uname() for pipe size modification checks
      doc: s/librelist.com/librelist.org/
      vmsplice: avoid referencing invalid stack address for strings
      vmsplice: more consistent fileno retry handling