labels: Warn if new label created on pass two
labels: Warn if new label created on pass two

When symbols are created turing non-first pass we
should at least warn a user since it's a sign of
potential problem.

http://bugzilla.nasm.us/show_bug.cgi?id=3392358

Signed-off-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@gmail.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm