GetColumns: Retrieve a set of columns widths from an anchor   [ 54 ]

This function enables a program to retrieve a set of float numbers supposed to be the column widths of a table to be built within target PDF document.

Developper Notes:

1. See Forms & Anchor page for a description of a column structure.
2. In SetColumn() instruction found within a form, it is a good practise to set the float numbers of unmeaningful columns to negative so that a program may easily find how many columns are assumed to be relevant for target table.