Fix AC_CHECK_ALIGNOF for HPUX

[Ralf Wildenhues]

OK to apply?  This fixes the corresponding test failures on HPUX 10.20
and 11.00.

Cheers,
Ralf

        * lib/autoconf/types.m4 (AC_CHECK_ALIGNOF): Work around
        HPUX compiler bug, similarly to AC_CHECK_SIZEOF, as documented
        in section `Specific Compiler Characteristics'.

Index: lib/autoconf/types.m4
===================================================================
RCS file: /cvsroot/autoconf/autoconf/lib/autoconf/types.m4,v
retrieving revision 1.31
diff -u -r1.31 types.m4
--- lib/autoconf/types.m4       14 May 2005 07:00:40 -0000      1.31
+++ lib/autoconf/types.m4       2 Mar 2006 19:57:11 -0000
@@ -406,7 +406,9 @@
 AC_CHECK_TYPE([$1], [], [], [$2])
 AC_CACHE_CHECK([alignment of $1], AS_TR_SH([ac_cv_alignof_$1]),
 [if test "$AS_TR_SH([ac_cv_type_$1])" = yes; then
-  _AC_COMPUTE_INT([offsetof (struct { char x; $1 y; }, y)],
+  # The cast to long int works around a bug in the HP C Compiler,
+  # see AC_CHECK_SIZEOF for more information.
+  _AC_COMPUTE_INT([(long int) offsetof (struct { char x; $1 y; }, y)],
                  [AS_TR_SH([ac_cv_alignof_$1])],
                  [AC_INCLUDES_DEFAULT([$2])
 #ifndef offsetof