Add layouts for some PE models

PortableExecutable/RSDSProgramDatabase.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.InteropServices;
 
 namespace SabreTools.Models.PortableExecutable
 {
@@ -7,28 +8,30 @@ namespace SabreTools.Models.PortableExecutable
     /// or "DS" type which are emitted by Miscrosoft's link.exe from version 7 and above.
     /// </summary>
     /// <see href="http://www.godevtool.com/Other/pdb.htm"/>
+    [StructLayout(LayoutKind.Sequential)]
     public sealed class RSDSProgramDatabase
     {
         /// <summary>
         /// "RSDS" signature
         /// </summary>
-        public uint Signature { get; set; }
+        public uint Signature;
 
         /// <summary>
         /// 16-byte Globally Unique Identifier
         /// </summary>
-        public Guid GUID { get; set; }
+        public Guid GUID;
 
         /// <summary>
         /// Ever-incrementing value, which is initially set to 1 and
         /// incremented every time when a part of the PDB file is updated
         /// without rewriting the whole file. 
         /// </summary>
-        public uint Age { get; set; }
+        public uint Age;
 
         /// <summary>
         /// zero terminated UTF8 path and file name
         /// </summary>
-        public string? PathAndFileName { get; set; }
+        [MarshalAs(UnmanagedType.LPWStr)]
+        public string? PathAndFileName;
     }
 }