Patch Mono.Cecil to allow safe multi-threaded read access.

Mono.Cecil/Mono.Cecil/ModuleDefinition.cs

@@ -757,18 +757,22 @@ namespace Mono.Cecil {
 		{
 			return Read (this, (_, reader) => reader.LookupToken (token));
 		}
+		
+		readonly object module_lock = new object();
 
 		internal TRet Read<TItem, TRet> (TItem item, Func<TItem, MetadataReader, TRet> read)
 		{
-			var position = reader.position;
-			var context = reader.context;
+			lock (module_lock) {
+				var position = reader.position;
+				var context = reader.context;
 
-			var ret = read (item, reader);
+				var ret = read (item, reader);
 
-			reader.position = position;
-			reader.context = context;
+				reader.position = position;
+				reader.context = context;
 
-			return ret;
+				return ret;
+			}
 		}
 
 		void ProcessDebugHeader ()