dmeventd: fix typo in configure.in causing monitoring failure

Hi,

Attached patch fixes a typo in configure.in of device-mapper.

As a result of the typo, DMEVENTD_PATH in libdevmapper-event could be set ignoring "exec_prefix" and the monitoring may not work.

For example, LVM2 may complain it can't communicate with dmeventd:

# lvm.static lvcreate -m1 -l1 testvg
  Unable to read from event server.
  Unable to read from event server.
  testvg-lvol0: event registration failed: Input/output error
  testvg/lvol0: mirror segment monitoring function failed.
  Logical volume "lvol0" created

while in the background, dmeventd caused segfault soon after startup:

From syslog:
dmeventd[688]: dmeventd ready for processing.
kernel: dmeventd[688]: segfault at 08000000 eip 4ff615a7 esp bfafe2f8 error 4

Thanks,

Jun'ichi Nomura, NEC Corporation of America

Fix a typo in configure.in ("dmeventd_pref" should be "dmeventd_prefix")

As a result of this typo, LVM2 commands might try to invoke dmeventd which doesn't match to the library version and monitoring fails to work.

Index: device-mapper.work/configure.in
===================================================================
@@ -394,7 +394,7 @@ if test "$DMEVENTD" = yes; then
 	AC_ARG_WITH(dmeventd-path,
   		    [  --with-dmeventd-path=PATH       dmeventd path [[${exec_prefix}/sbin/dmeventd]] ],
   		    [ AC_DEFINE_UNQUOTED(DMEVENTD_PATH,"$withval") ],
-  		    [ AC_DEFINE_UNQUOTED(DMEVENTD_PATH,"$dmeventd_pref/sbin/dmeventd") ])
+  		    [ AC_DEFINE_UNQUOTED(DMEVENTD_PATH,"$dmeventd_prefix/sbin/dmeventd") ])
 fi
 ################################################################################
 AC_SUBST(usrlibdir)

Index: device-mapper.work/configure
===================================================================
@@ -6646,7 +6646,7 @@ _ACEOF
 
 else
    cat >>confdefs.h <<_ACEOF
-#define DMEVENTD_PATH "$dmeventd_pref/sbin/dmeventd"
+#define DMEVENTD_PATH "$dmeventd_prefix/sbin/dmeventd"
 _ACEOF
 
 fi