Compile .l files (flex) with the waf rule at runtime

Compile .l files (flex) with the waf rule at runtime

Other parts of Samba already compile these directly.

This makes these files compile with modern compiler warnings.

The primary difference (other than being built with a newer
flex) is the loss of the #include "config.h" but
this is not used in the other .l files elsewehre and does not
seem to matter on modern systems.

The generated output from compile_et asn1_compile has not changed
(so I think the hx509 case is safe).

The mdssvc case just has changed file locations and line numbers.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>