[do_jdbc] Add ability to get use Reader#row_count. That value is obtained during executing reader using scrollable RS if driver supports that. The only jdbc driver doesn't support scrollable RS is SQLite3. Drivers that don't provide scrollable RS use dirty trick/hack to obtain numer of rows. I think counting rows should be moved to row_count method and numer of rows should be counted only in first invocation of row_count method (lazily). Programmers that use cursor (Reader#next) don't need to know number of rows.
[do_jdbc] Add ability to get use Reader#row_count. That value
is obtained during executing reader using scrollable RS if
driver supports that. The only jdbc driver doesn't support
scrollable RS is SQLite3. Drivers that don't provide
scrollable RS use dirty trick/hack to obtain numer of rows.
I think counting rows should be moved to row_count method and
numer of rows should be counted only in first invocation of
row_count method (lazily). Programmers that use cursor (Reader#next)
don't need to know number of rows.

Signed-off-by: Alex Coles <60c6d277a8bd81de7fdde19201bf9c58a3df08f4@alexcolesportfolio.com>
simonkro/do_mysql,simonkro/do_mysql,simonkro/do_mysql