ESM4 reader skips last record in content files

The ESM4 reader's getRecordHeader() function adds the entire record's size to the context's fileRead counter as soon as it runs. This makes the check in readerutils.hpp return one record early.

This ESM4 ESP has two NPC_ records, but esmtool.exe dumps one:

.\esmtool dump ESM4LastRecordSkipped.esp

Using default (English) font encoding.
Loading TES4 file: "ESM4LastRecordSkipped.esp"
Author: OpenMW test
Description: The last record in this file is never read
File format version: 1.71
Masters:
  Morrowind.esm, 0 bytes

Group: RecordType GRUP

  Record: NPC_
  Id: 0x800
  Record flags: [None] (0x00000000)
  EditorId: TestFirstNpc
  FullName:
  Model:
  Kf:
  Data:  ?

ESM4LastRecordSkipped.esp