Auto merge of #2334 - rtzoeller:netbsd_sched_consts, r=JohnTitor

Add scheduler constants for NetBSD

FreeBSD-like platforms also define `SCHED_OTHER`, `SCHED_FIFO`, and `SCHED_RR`, but with different numeric values.

Author: bors

libc-test/semver/netbsd.txt

@@ -792,6 +792,10 @@ RUN_LVL
 RUSAGE_CHILDREN
 RUSAGE_SELF
 SCALE_PPM
+SCHED_FIFO
+SCHED_NONE
+SCHED_OTHER
+SCHED_RR
 SCM_CREDS
 SCM_RIGHTS
 SCM_TIMESTAMP

src/unix/bsd/netbsdlike/netbsd/mod.rs

@@ -1532,6 +1532,11 @@ pub const PTHREAD_MUTEX_ERRORCHECK: ::c_int = 1;
 pub const PTHREAD_MUTEX_RECURSIVE: ::c_int = 2;
 pub const PTHREAD_MUTEX_DEFAULT: ::c_int = PTHREAD_MUTEX_NORMAL;
 
+pub const SCHED_NONE: ::c_int = -1;
+pub const SCHED_OTHER: ::c_int = 0;
+pub const SCHED_FIFO: ::c_int = 1;
+pub const SCHED_RR: ::c_int = 2;
+
 pub const EVFILT_AIO: u32 = 2;
 pub const EVFILT_PROC: u32 = 4;
 pub const EVFILT_READ: u32 = 0;