Auto merge of #2281 - devnexen:fbsd_map_excl, r=JohnTitor

freebsd add MAP_EXCL, with MAP_FIXED is equivalent to Linux's MAP_FIX…

…ED_NOREPLACE

Author: bors

libc-test/semver/freebsd.txt

@@ -646,6 +646,7 @@ MADV_RANDOM
 MADV_SEQUENTIAL
 MADV_WILLNEED
 MAP_COPY
+MAP_EXCL
 MAP_FILE
 MAP_HASSEMAPHORE
 MAP_NOCORE

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

@@ -507,6 +507,7 @@ pub const Q_GETQUOTA: ::c_int = 0x700;
 pub const Q_SETQUOTA: ::c_int = 0x800;
 
 pub const MAP_GUARD: ::c_int = 0x00002000;
+pub const MAP_EXCL: ::c_int = 0x00004000;
 pub const MAP_ALIGNED_SUPER: ::c_int = 1 << 24;
 
 pub const POSIX_FADV_NORMAL: ::c_int = 0;