optimize: use LuaJIT v2.1's new table.new API to optimize Lua table allocations. when table.new is missing, just fall back to the good old "{}". this gives 12% overall speedup for a typical result set with 500 rows. feature: added an optional new argument "est_rows" to the query() and read_result() methods.
docs: documented the new optional argument "est_nrows" to the query() and read_result() methods.