Add a "README.hpux" file, giving notes about the Software Porting And

Add a "README.hpux" file, giving notes about the Software Porting And
Archive Centre for HP-UX, who have (perhaps not the latest version of)
Ethereal in their archives, and the HP-UX C compiler options they used
when building their version.

Also note in the "README.hpux" file that there are, in the "INSTALL"
file for "libpcap", several comments about HP-UX that should be read if
you're going to use Ethereal with "libpcap" to capture packets.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@1159 f5534014-38df-0310-8fa8-9805f1628bb7