build: drop unused <sys/syslimits.h> header

<sys/syslimits.h> is not standardized, so portable programs should
not need to rely on it.  If there really is something that we need
where <sys/syslimits.h> provided the limit but <limits.h> did not,
then that would be a candidate for fixing in gnulib.  But this patch
did not turn up any compilation failures on Linux.

* src/internal.h (includes): Drop unused header.
* daemon/libvirtd.h (includes): Likewise.
* configure.ac (AC_CHECK_HEADERS): Likewise.
Based on a report by Matthias Bolte.

configure.ac

@@ -133,7 +133,7 @@ AC_CHECK_FUNCS([pthread_sigmask pthread_mutexattr_init])
 LIBS=$old_libs
 
 dnl Availability of various common headers (non-fatal if missing).
-AC_CHECK_HEADERS([pwd.h paths.h regex.h sys/syslimits.h sys/un.h \
+AC_CHECK_HEADERS([pwd.h paths.h regex.h sys/un.h \
   sys/poll.h syslog.h mntent.h net/ethernet.h linux/magic.h \
   sys/un.h sys/syscall.h])
 

daemon/libvirtd.h

@@ -38,10 +38,6 @@
 #  include <dbus/dbus.h>
 # endif
 
-# ifdef HAVE_SYS_SYSLIMITS_H
-#  include <sys/syslimits.h>
-# endif
-
 # include <rpc/types.h>
 # include <rpc/xdr.h>
 # include "remote_protocol.h"

src/internal.h

@@ -18,10 +18,6 @@
 #  define sa_assert(expr) /* empty */
 # endif
 
-# ifdef HAVE_SYS_SYSLIMITS_H
-#  include <sys/syslimits.h>
-# endif
-
 /* The library itself is allowed to use deprecated functions /
  * variables, so effectively undefine the deprecated attribute
  * which would otherwise be defined in libvirt.h.