Merge #763

763: Add opcode and flag enums to dns export r=Dirbaio a=wmcleish

Added opcode and flag enums to dns export. As it currently stands, user is not able to access the enums which are parameters to DnsPacket's "set_opcode" and "set_flags" functions. This change will allow the user to import and use those enums to set the packet contents. If there is a more elegant way to include them in DnsPacket instead of being their own imports, please suggest what changes can be made. Refer to [issue 762](https://github.com/smoltcp-rs/smoltcp/issues/762)

Edit: Sorry for commit spam, rustfmt not working locally for some reason.

Co-authored-by: Will McLeish <71392578+wmcleish@users.noreply.github.com>

src/wire/mod.rs

@@ -251,7 +251,10 @@ pub use self::dhcpv4::{
 };
 
 #[cfg(feature = "proto-dns")]
-pub use self::dns::{Packet as DnsPacket, Repr as DnsRepr, Type as DnsQueryType};
+pub use self::dns::{
+    Flags as DnsFlags, Opcode as DnsOpcode, Packet as DnsPacket, Repr as DnsRepr,
+    Type as DnsQueryType,
+};
 
 /// Parsing a packet failed.
 ///