extract_links.c: Use a larger x_table for long sentences
extract_links.c: Use a larger x_table for long sentences

The size of the x_table is much less critical to performance than
the size of Table_connector (used by do_count()), because it has much
less accesses. However, the number of entries per bucket become
very high for long sentences and causes a performance problem.

opencog/link-grammar,ampli/link-grammar,opencog/link-grammar,ampli/link-grammar,opencog/link-grammar,ampli/link-grammar,linas/link-grammar,opencog/link-grammar,linas/link-grammar,linas/link-grammar,linas/link-grammar,linas/link-grammar,linas/link-grammar,ampli/link-grammar,linas/link-grammar,opencog/link-grammar,opencog/link-grammar,ampli/link-grammar,ampli/link-grammar,ampli/link-grammar,opencog/link-grammar,linas/link-grammar,ampli/link-grammar,ampli/link-grammar,opencog/link-grammar,linas/link-grammar,opencog/link-grammar