EXPERIMENTAL modify_for_hpux_build.

environment: HP-UX 11.31 ia64, gcc 4.7.1(HP AllianceOne version) or HP C/aC++

modified 3 files.

- configure.ac - add hpux section.
- crypto/Makefile.am.tpl - add hpux section.
- crypto/compat/arc4random.h - add hpux section.

added 3 files.

- crypto/compat/arc4random_hpux.h - same as arc4random_solaris.h

- crypto/compat/getentropy_hpux.c - based on getentropy_solaris.c
  change including  sys/sha2.h to openssl/sha.h
  remove defining SHA512_...
  remove including link.h, sys/statfs.h, sys/loadavg.h
  add including sys/pstat.h
  in getentropy_urandom() routine,
   - checking /dev/urandom only
  in getentropy_fallback() routine,
   - using sysconf(_SC_PAGESIZE) instead of getpagesize()
   - using pstat_getprocvm() instead of dl_iterate_phdr()[*]
   - using pstat_getdynamic() instead of getloadavg()[*]
  [*] I'm using alternate system calls, because
      hpux doesn't have dl_iterate_phdr() and getloadavg().

- crypto/compat/issetugid_hpux.c - using pstat_getproc() and get*id()
  hpux doesn't have issetugid(), and this is sample implementation.
  this should be verified.