C#: Always use the unbound type declaration location for type location.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/Type.qll

@@ -30,7 +30,7 @@ class Type extends Member, TypeContainer, @type {
   /** Holds if this type is implicitly convertible to `that` type. */
   predicate isImplicitlyConvertibleTo(Type that) { implicitConversion(this, that) }
 
-  override Location getALocation() { type_location(this, result) }
+  override Location getALocation() { type_location(this.getUnboundDeclaration(), result) }
 
   override Type getChild(int n) { none() }