hppa: update error codes and signal numbers

hppa: update error codes and signal numbers

There are two important changes in here:

1. EWOULDBLOCK has been up to kernel 3.14 errorcode #246. Since hppa
folks had problems with EWOULDBLOCK != EAGAIN, this was changed in
kernel 3.14.

2. Starting with kernel 3.18, hppa folks changed some signal numbers in
such a way that we end up with SIGRTMIN == 32, which brings hppa in sync
with other linux ports.

Both were incompatible changes which basically broke hppa ABI, but since
they have been merged into the kernel, we have to follow.