Hide AH_HOOK behind AH_DEFUN.

Hide AH_HOOK behind AH_DEFUN.

* autoheader.m4 (AH_DEFUN): New macro.  Combination of define and
AH_HOOK.
(AC_TRY_RUN, AC_DEFINE, AC_DEFINE_UNQUOTED, AC_CHECK_LIB,
AC_CHECK_HEADERS, AC_CHECK_HEADERS_DIRENT, AC_CHECK_DECLS,
AC_CHECK_FUNCS, AC_CHECK_SIZEOF, AC_PROG_LEX, AC_CHECK_MEMBERS,
AC_CHECK_TYPE, AC_FUNC_ALLOCA, AC_CHECK_TYPES, AC_C_CHAR_UNSIGNED,
AC_AIX, AC_F77_WRAPPERS, AC_CONFIG_HEADER): All the former calls
to define and AH_HOOK in autoheader.m4 are replaced by AH_DEFUN.