Fixed broken link (dotnet#2745)

* Fixed broken link

* Fixed additional broken xref

* Fixed link

Author: Ron Petrusha

xml/System.Runtime.InteropServices/NativeLibrary.xml

@@ -136,8 +136,8 @@ This is a simple wrapper around OS calls and does not perform any name mangling.
 Given a library name, this method searches specific paths based on the  runtime configuration, input parameters, and attributes of the calling assembly. If the `searchPath` parameter is non-null, the flags in this enumeration are used. Otherwise, the flags specified by the <xref:System.Runtime.InteropServices.DefaultDllImportSearchPathsAttribute> on the calling assembly, if any are present, are used. This method does not invoke the following managed callbacks for native library resolution: 
 
 - The per-assembly registered callback.
-- <xref:System.Runtime.Loader.AssemblyLoadContext.LoadUnmanagedDll%2A?displayProperty=nameWithType>.
-- <xref:System.Runtime.Loader.AssemblyLoadContext.ResolvingUnmanagedDllEvent?displayProperty=nameWithType>.
+- The <xref:System.Runtime.Loader.AssemblyLoadContext.LoadUnmanagedDll%2A?displayProperty=nameWithType> method.
+- The <xref:System.Runtime.Loader.AssemblyLoadContext.ResolvingUnmanagedDll?displayProperty=nameWithType> event.
 
          ]]></format>
          </remarks>

xml/System.Runtime.Loader/AssemblyLoadContext.xml

@@ -836,8 +836,14 @@ Each <xref:System.Runtime.Loader.AssemblyLoadContext> can load only:
         <ReturnType>System.Func&lt;System.Reflection.Assembly,System.String,System.IntPtr&gt;</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <remarks>To be added.</remarks>
+        <summary>Occurs when the resolution of a native library fails.</summary>
+        <remarks>  
+          <format type="text/markdown"><![CDATA[  
+
+This event is raised if the native library cannot be resolved by the default resolution logic (including <xref:System.Runtime.Loader.AssemblyLoadContext.LoadUnmanagedDll%2A>).
+
+         ]]></format>
+         </remarks>
       </Docs>
     </Member>
     <Member MemberName="SetProfileOptimizationRoot">