fetching a query with more than 250 columns triggers an assertion

[schveiguy]

An old assertion seems to be incorrect. Simple test case:

auto conn = new Connection(...);
auto sql = format("SELECT 1 as `%-(%s`, 1 as `%)`",
		iota(26*26).map!(i => [cast(char)(i / 26 + 'A'), cast(char)(i % 26 + 'A')]));
auto result = con.query(sql);

Assertion is here:

mysql-native/source/mysql/protocol/comms.d

Line 492 in fa4d3fb

assert(packet.front >= 1 && packet.front <= 250); // Result set packet header should have this value

This number is the field count, and is a length encoded integer, which is fine to be greater than 250 (it can be all the way up to 2^64 theoretically). I believe it's not OK to be 0 though.