Auto merge of rust-lang#703 - mneumann:dragonfly-add-evfilt-except, r=alexcrichton

Add EVFILT_EXCEPT constant

Author: bors

src/unix/bsd/freebsdlike/dragonfly/mod.rs

@@ -340,6 +340,7 @@ pub const EVFILT_VNODE: ::int16_t = -4;
 pub const EVFILT_PROC: ::int16_t = -5;
 pub const EVFILT_SIGNAL: ::int16_t = -6;
 pub const EVFILT_TIMER: ::int16_t = -7;
+pub const EVFILT_EXCEPT: ::int16_t = -8;
 pub const EVFILT_USER: ::int16_t = -9;
 pub const EVFILT_FS: ::int16_t = -10;