*.natvis: Use s8 postfixes to correctly interpret rust strings as UTF-8.

Author: MaulingMonkey

Diff for: src/etc/natvis/intrinsic.natvis

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
   <Type Name="str">
-    <DisplayString>{data_ptr,[length]}</DisplayString>
-    <StringView>data_ptr,[length]</StringView>
+    <DisplayString>{data_ptr,[length]s8}</DisplayString>
+    <StringView>data_ptr,[length]s8</StringView>
     <Expand>
       <Item Name="[size]" ExcludeView="simple">length</Item>
       <ArrayItems>

Diff for: src/etc/natvis/liballoc.natvis

@@ -42,8 +42,8 @@
     </Expand>
   </Type>
   <Type Name="alloc::string::String">
-    <DisplayString>{*(char**)this,[vec.len]}</DisplayString>
-    <StringView>*(char**)this,[vec.len]</StringView>
+    <DisplayString>{*(char**)this,[vec.len]s8}</DisplayString>
+    <StringView>*(char**)this,[vec.len]s8</StringView>
     <Expand>
       <Item Name="[size]" ExcludeView="simple">vec.len</Item>
       <Item Name="[capacity]" ExcludeView="simple">vec.buf.cap</Item>