Merge from vendor branch TNF:

Merge from vendor branch TNF:
Initial import of converters/xlreader (version 0.9.0)

Read data from Excel spread sheets without Microsoft!
Provides an API to allow any application to read Excel
documents. Demo interface converts data to tab
delimited, CSV or SQL inserts. Written in C. Based on
the the Java version by Andrew Khan.

Provided by David Forrai <david.forrai@gemair.com> in PR#21103,
slightly modified by me. Thanks!