Fix incorrect output of configure summary when the compiler is
configured with concurrency.

https://github.com/uniconproject/unicon/commit/718e953063849d7f08f74e15746521354bd36a0e
--- configure.ac
+++ configure.ac
@@ -993,7 +993,7 @@ fi
 
 if test "x$iconc"  = "xyes" || test "x$iconc" = "xon" ; then
   if test "x$coniconc"      = "xyes" ; then
-     echo " + Compiler: with concurrency >> unicon-config.log"
+     echo " + Compiler: with concurrency" >> unicon-config.log
   else
      echo " + Compiler: no concurrency" >> unicon-config.log
   fi