Read file content in case mmap fails (fallback).

Task-number: QTIFW-400

Change-Id: Ic1bc25b7bc1ada6b12b7967c4c41e65f64e81267
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Niels Weber <niels.weber@digia.com>