setup_once.h: HP-UX <sys/socket.h> issue workaround

Issue: When building a 32bit target with large file support HP-UX
<sys/socket.h> header file may simultaneously provide two different
sets of declarations for sendfile and sendpath functions, one with
static and another with external linkage. Given that we do not use
mentioned functions we really don't care which linkage is the
appropriate one, but on the other hand, the double declaration emmits
warnings when using the HP-UX compiler and errors when using modern
gcc versions resulting in fatal compilation errors.

Mentioned issue is now fixed as long as we don't use sendfile nor
sendpath functions.

lib/setup_once.h

@@ -87,10 +87,30 @@
 #include <unistd.h>
 #endif
 
+#ifdef __hpux
+#  if !defined(_XOPEN_SOURCE_EXTENDED) || defined(_KERNEL)
+#    ifdef _APP32_64BIT_OFF_T
+#      define OLD_APP32_64BIT_OFF_T _APP32_64BIT_OFF_T
+#      undef _APP32_64BIT_OFF_T
+#    else
+#      undef OLD_APP32_64BIT_OFF_T
+#    endif
+#  endif
+#endif
+
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
 #endif
 
+#ifdef __hpux
+#  if !defined(_XOPEN_SOURCE_EXTENDED) || defined(_KERNEL)
+#    ifdef OLD_APP32_64BIT_OFF_T
+#      define _APP32_64BIT_OFF_T OLD_APP32_64BIT_OFF_T
+#      undef OLD_APP32_64BIT_OFF_T
+#    endif
+#  endif
+#endif
+
 
 /*
  * Definition of timeval struct for platforms that don't have it.