Auto merge of #2979 - redox-os:redox-0.2.136, r=JohnTitor

Add MADV constants for Redox

Required for `memmap2` crate

Author: bors

libc-test/semver/redox.txt

@@ -100,6 +100,11 @@ IPV6_ADD_MEMBERSHIP
 IPV6_DROP_MEMBERSHIP
 IUCLC
 IUTF8
+MADV_DONTNEED
+MADV_NORMAL
+MADV_RANDOM
+MADV_SEQUENTIAL
+MADV_WILLNEED
 MSG_DONTWAIT
 NI_DGRAM
 NI_MAXSERV

src/unix/redox/mod.rs

@@ -634,6 +634,12 @@ pub const PROT_READ: ::c_int = 0x0004;
 pub const PROT_WRITE: ::c_int = 0x0002;
 pub const PROT_EXEC: ::c_int = 0x0001;
 
+pub const MADV_NORMAL: ::c_int = 0;
+pub const MADV_RANDOM: ::c_int = 1;
+pub const MADV_SEQUENTIAL: ::c_int = 2;
+pub const MADV_WILLNEED: ::c_int = 3;
+pub const MADV_DONTNEED: ::c_int = 4;
+
 pub const MAP_SHARED: ::c_int = 0x0001;
 pub const MAP_PRIVATE: ::c_int = 0x0002;
 pub const MAP_ANON: ::c_int = 0x0020;