Bugfix for "Unable to find startxref" exception

[unixnut]

Type of pull request

• [Y] Bug fix (involves code and configuration changes)
• [ ] New feature (involves code and configuration changes)
• [ ] Documentation update
• [ ] Something else

About

Addresses inadequacies in handling startxref statement before EOF marker.

Currently, getXrefData() uses a regex that requires a newline before the offset value.

This fix allows:

• space before the reference offset.
• keyword and offset on the same line (e.g. containing "startxref 1746580").

For more detail see #756

TO DO

• tests
• example files