use sigar_open instead of sigar_new wrapper

bindings/dotnet/default.build

@@ -25,6 +25,7 @@
     <mkdir dir="${build.dir}"/>
 
     <csc target="library" debug="${debug}"
+         unsafe="true"
          output="${sigarsharp}">
       <sources>
         <includes name="src/Sigar.cs"/>

bindings/dotnet/src/Sigar.cs

@@ -31,13 +31,16 @@ namespace Hyperic.Sigar {
         internal HandleRef sigar;
 
         [DllImport(LIBSIGAR)]
-        private static extern IntPtr sigar_new();
+        unsafe private static extern int sigar_open(IntPtr *sigar);
 
         [DllImport(LIBSIGAR)]
         private static extern int sigar_close(IntPtr sigar);
 
         public Sigar() {
-            IntPtr handle = sigar_new();
+            IntPtr handle;
+            unsafe { //&pointers are considered "unsafe"
+                sigar_open(&handle);
+            }
             this.sigar = new HandleRef(this, handle);
         }