HP-UX needs sys/pstat.h for missing/setproctitle.c

Check for HAVE_SYS_PSTAT_H is already in place so only request to check for sys/pstat.h in configure.

Signed-off-by: Michal Rokos <rokos@nextsoft.cz>

diff --git a/configure.in b/configure.in
index 381dfd3..bc6855d 100644
--- a/configure.in
+++ b/configure.in
@@ -1616,6 +1616,7 @@ AS_CASE(["$target_os"],
 [aix* | k*bsd*-gnu | kopensolaris*-gnu | linux* | darwin*], [AC_DEFINE(SPT_TYPE,SPT_REUSEARGV)],
 [hpux*], [AC_DEFINE(SPT_TYPE,SPT_PSTAT) ],
 [])
+AC_CHECK_HEADERS(sys/pstat.h)
 
 
 AC_CACHE_CHECK(for signbit, rb_cv_have_signbit,