Update branch projects to use NUnit 2.5.8.
diff --git a/nant.build b/nant.build
index ae0f0ea..fa3e756 100644
--- a/nant.build
+++ b/nant.build
@@ -62,7 +62,7 @@
         <!-- Property grouping for 'vendor.nunit.org' -->
         <property name="vendor.nunit.org.name" value="NUnit" />
         <property name="vendor.nunit.org.group" value="org.nunit" />
-        <property name="vendor.nunit.org.version" value="2.5.5" />
+        <property name="vendor.nunit.org.version" value="2.5.8" />
         <property name="vendor.nunit.org.filenames" value="nunit.framework.dll" />
 
         <!-- Property grouping for 'vendor.nunit.org' -->