Add some basic detection of restartable syscalls, sigaction,

socketpair.  Use dependent on useful detection is.

acconfig.h

@@ -1,4 +1,3 @@
-/* $OpenLDAP$ */
 /*
  * Copyright 1998,1999 The OpenLDAP Foundation, Redwood City, California, USA
  * All rights reserved.

configure.in

@@ -639,12 +639,15 @@ dnl hopefully we won't include too many libraries
 
 dnl require select
 AC_CHECK_FUNC(select, :, AC_MSG_ERROR([select() required.]))
+AC_CHECK_FUNCS(socketpair)
 
 dnl Select arg types
 dnl (if this detection becomes permenent, it and the select() detection
 dnl should be done before the yielding select test) 
 AC_FUNC_SELECT_ARGTYPES
 
+dnl check to see if system call automatically restart
+AC_SYS_RESTARTABLE_SYSCALLS
 
 dnl require POSIX regex
 AC_CHECK_HEADERS( regex.h )
@@ -1844,6 +1847,7 @@ AC_CHECK_FUNCS(		\
 	setsid			\
 	setuid			\
 	seteuid			\
+	sigaction		\
 	signal			\
 	sigset			\
 	snprintf		\

include/portable.h.in

@@ -34,6 +34,10 @@
 /* Define if you don't have vprintf but do have _doprnt.  */
 #undef HAVE_DOPRNT
 
+/* Define if system calls automatically restart after interruption
+   by a signal.  */
+#undef HAVE_RESTARTABLE_SYSCALLS
+
 /* Define if your struct stat has st_blksize.  */
 #undef HAVE_ST_BLKSIZE
 
@@ -261,6 +265,9 @@
 /* Define if you have the setuid function.  */
 #undef HAVE_SETUID
 
+/* Define if you have the sigaction function.  */
+#undef HAVE_SIGACTION
+
 /* Define if you have the signal function.  */
 #undef HAVE_SIGNAL
 
@@ -270,6 +277,9 @@
 /* Define if you have the snprintf function.  */
 #undef HAVE_SNPRINTF
 
+/* Define if you have the socketpair function.  */
+#undef HAVE_SOCKETPAIR
+
 /* Define if you have the strdup function.  */
 #undef HAVE_STRDUP