Change default expansion behaviour for tables to doubling

[jeromekelleher]

The C tables currently have a mechanism for incrementing the available size using a constant value. The default is to expand with a fixed size of 1024 rows. This should be changed to default to doubling on demand as follows: if the max_rows_increment value is 0, we double the number of rows (or increase the size to the requested, whichever is larger). This should be efficient in most cases, and also give good flexibility for those who want to tightly control memory usage and realloc behaviour.