Casting resultset to native PHP types

[codercms]

According to this PR - php/php-src#4939

[codercms]

@twose could you review this PR?
This PR makes Postgres Client to return values in native PHP types instead of only strings.

[twose]

@yunnian is the author of ext-PostgreSQL

and call @matyhtf and @huanghantao too

anyway, it looks good to me, thank you for your contribution

[yunnian]

Let's discuss whether it's better to add an option, such as：

$mysqli->options(MYSQLI_OPT_INT_AND_FLOAT_NATIVE, 1);

[codercms]

@yunnian do we have any reasons to add custom parameter that toggles float/int conversion?
P.S. Perhaps we can add custom parameter that will toggle casting from PostgreSQL types to PHP native types.