select.c: Pass arena to eval_expression

We might need buffers for string concatenation or operations on arrays.  The
arena initialization/freeing code was moved to the outer loop, so that we get
one arena per row.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
select.c: Allocate sufficiently large buffer for time_float4 formatting

We were 2 bytes short, so that -FLT_MIN would overflow our output buffer,
leading to occasional crashes.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
Support the SQL:2008 "OFFSET n FETCH NEXT n ONLY" syntax

This syntax can now be used to limit the output of SELECT statements.  For now,
we are limited to integer offsets and limits rather than full expressions.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>
query-parser.y: Fix grammar for forcing ; at the end of statements

Previously, an unexpected token could start a statement if it was preceded by a
valid statement.

Signed-off-by: Morten Hustveit <morten.hustveit@gmail.com>