scanner: fix reading of really long line

scanner: fix reading of really long line

Current code is causing a failure in adding a set containing
a really long list of elements. The failure occurs as soon as
the line is longer than flex read buffer.

When a line is longer than scanner buffer size, the code in YY_INPUT
forces a rewind to the beginning of the string because it does not
find a end of line. The result is that the string is never parsed.

This patch updates the code by rewinding till we found a space.

Signed-off-by: Eric Leblond <eric@regit.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>