Auto merge of #865 - cactorium:master, r=alexcrichton

Minor fixes for mips-unknown-linux-uclibc

Just adding a few definitions so the toolchain compiles

Author: bors

src/unix/uclibc/mips/mips32.rs

@@ -66,7 +66,7 @@ s! {
     }
 
     pub struct sigaction {
-        pub sa_flags: ::c_uint,
+        pub sa_flags: ::c_int,
         pub sa_sigaction: ::sighandler_t,
         pub sa_mask: sigset_t,
         _restorer: *mut ::c_void,

src/unix/uclibc/mod.rs

@@ -790,6 +790,8 @@ pub const IP_TTL: ::c_int = 2;
 pub const IP_HDRINCL: ::c_int = 3;
 pub const IP_ADD_MEMBERSHIP: ::c_int = 35;
 pub const IP_DROP_MEMBERSHIP: ::c_int = 36;
+pub const IPV6_ADD_MEMBERSHIP: ::c_int = 20;
+pub const IPV6_DROP_MEMBERSHIP: ::c_int = 21;
 
 pub const IPV6_JOIN_GROUP: ::c_int = 20;
 pub const IPV6_LEAVE_GROUP: ::c_int = 21;