doc/Platforms.txt: ngircd builds on hppa2.0w-hp-hpux11.11 target

doc/Platforms.txt: ngircd builds on hppa2.0w-hp-hpux11.11 target

Goetz Hoffart reports successful compile on HPUX/HPPA (on ngircd mailing list):

             Target: hppa2.0w-hp-hpux11.11
           Compiler: gcc
     Compiler flags: -g -O2 -pipe -W -Wall -Wpointer-arith -Wstrict-prototypes -fstack-protector -D_XOPEN_SOURCE_EXTENDED
-DSYSCONFDIR='"$(sysconfdir)"'
          Libraries: -lz -lnsl

     Syslog support: yes     Enable debug code: no
   zlib compression: yes           IRC sniffer: no
   Use TCP Wrappers: no        Strict RFC mode: no
   Zeroconf support: no          IRC+ protocol: yes
      IDENT support: no            I/O backend: "poll()"
      IPv6 protocol: no            SSL support: no