Allow build on HP-UX 11.X

Patch from Richard Lloyd (slightly edited from me), following the list
of changes as described by the author:

src/Makefile:
- Added PREFIX and BINDIR for the install: rule.
- Added a "make hpux" line to the help: rule.
- Added "make test"/"make check" rule that runs the $(PGOBENCH) command.
- "make clean" now additionally removes core and bench.txt.
- Added an hpux: rule.
- Added an install: rule to mkdir $(BINDIR), copy $(EXE) to $(BINDIR) and
 then strip it.
- "make strip" now ensures that $(EXE) is built first before trying to
 strip it.
- Hide errors and output from the g++ command used by the .depend: rule and
 then touch .depend in case g++ isn't available.
- Hide errors from the "include .depend" in case .depend doesn't exist
 (e.g. directly after a "make clean").

src/book.cpp and src/book.h:
- HP-UX's aCC really didn't like the const keywords used for the
 Book::file_name() definitions, so they were removed. I checked that this
 didn't affect a Linux build and it was still fine.

src/misc.cpp:
- HP-UX uses <sys/pstat.h> and pstat_getdynamic() to determine the number of
 CPU cores, so added conditional code for that (if pstat_getdynamic() fails,
 set the number of cores to 1).

src/tt.cpp:
- <xmmintrin.h> and _mm_prefetch() seem highly specific to the Intel x86(_64)
 and gcc platforms - neither exist in HP-UX, so conditionally avoid that
 code in HP-UX's case. Perhaps some sort of define is needed here
 such as -DHAS_MM_PREFETCH that could be #ifdef'ed for instead?

Even after these changes, it's more convenient for HP-UX users to edit the
default: rule in the Makefile to run "$(MAKE) hpux" before they build
stockfish, but that's not a big deal if they're warned about that first (the
same applies to all other builds other than the standard "$(MAKE) gcc" one).

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/tt.cpp

@@ -25,7 +25,9 @@
 #include <cassert>
 #include <cmath>
 #include <cstring>
-#include <xmmintrin.h>
+#if !defined(__hpux)
+#  include <xmmintrin.h>
+#endif
 
 #include "movegen.h"
 #include "tt.h"
@@ -167,11 +169,14 @@ TTEntry* TranspositionTable::retrieve(const Key posKey) const {
 /// to be loaded from RAM, that can be very slow. When we will
 /// subsequently call retrieve() the TT data will be already
 /// quickly accessible in L1/L2 CPU cache.
+#if defined(__hpux)
+void TranspositionTable::prefetch(const Key) const {} // Not supported on HP UX
+#else
 
 void TranspositionTable::prefetch(const Key posKey) const {
 
 #if defined(__INTEL_COMPILER) || defined(__ICL)
-   // This hack prevents prefetches to be optimized away by the
+   // This hack prevents prefetches to be optimized away by
    // Intel compiler. Both MSVC and gcc seems not affected.
    __asm__ ("");
 #endif
@@ -181,6 +186,7 @@ void TranspositionTable::prefetch(const Key posKey) const {
   _mm_prefetch(addr+64, _MM_HINT_T2); // 64 bytes ahead
 }
 
+#endif
 
 /// TranspositionTable::new_search() is called at the beginning of every new
 /// search. It increments the "generation" variable, which is used to