Don't install a SIGPIPE handler
Don't install a SIGPIPE handler

The default `SIGPIPE` handler installed by `TUnixSystem` does not do
anything except print a message and possibly causing an endless loop of
`SIGPIPE` handling:

```
echo 'std::cout << "foo" << std::endl;' | root -l |& true
python -c 'import ROOT; print "foo"' |& true
```

This fixes ROOT-4568 and ROOT-7659.

gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root,gganis/root