Auto merge of #2200 - aym-v:aym/expose-tos-and-recv-tos-fuschia, r=Amanieu

fuschia: add IP_TOS and IP_RECVTOS APIs

Needed to enable fuschia support on rust-lang/socket2#224

See [the fuschia header](https://cs.opensource.google/fuchsia/fuchsia/+/master:zircon/third_party/ulib/musl/include/netinet/in.h;l=181;bpv=1;bpt=1) for reference

Author: bors

libc-test/semver/fuchsia.txt

@@ -372,6 +372,8 @@ IPPROTO_UDPLITE
 IPV6_ADD_MEMBERSHIP
 IPV6_DROP_MEMBERSHIP
 IP_FREEBIND
+IP_TOS
+IP_RECVTOS
 IP_HDRINCL
 IP_TRANSPARENT
 ITIMER_PROF

src/fuchsia/mod.rs

@@ -1768,8 +1768,10 @@ pub const SCM_TIMESTAMP: ::c_int = SO_TIMESTAMP;
 pub const SOCK_RAW: ::c_int = 3;
 pub const SOCK_RDM: ::c_int = 4;
 
+pub const IP_TOS: ::c_int = 1;
 pub const IP_TTL: ::c_int = 2;
 pub const IP_HDRINCL: ::c_int = 3;
+pub const IP_RECVTOS: ::c_int = 13;
 pub const IP_FREEBIND: ::c_int = 15;
 pub const IP_TRANSPARENT: ::c_int = 19;
 pub const IP_MULTICAST_IF: ::c_int = 32;