Auto merge of #1186 - glaubitz:fcntl-fixes, r=alexcrichton

Define missing F_RDLCK, F_WRLCK and F_UNLCK constants on linux-mips -and s390x

These are defined in the fcntl.h glibc header on MIPS and s390x
systems on Linux but missing in the libc crate, so add them as they
are required for the file locking API in rustc.

Author: bors

src/unix/notbsd/linux/mips/mod.rs

@@ -537,6 +537,9 @@ pub const MAP_HUGETLB: ::c_int = 0x080000;
 
 pub const EFD_NONBLOCK: ::c_int = 0x80;
 
+pub const F_RDLCK: ::c_int = 0;
+pub const F_WRLCK: ::c_int = 1;
+pub const F_UNLCK: ::c_int = 2;
 pub const F_GETLK: ::c_int = 14;
 pub const F_GETOWN: ::c_int = 23;
 pub const F_SETOWN: ::c_int = 24;

src/unix/notbsd/linux/s390x.rs

@@ -791,6 +791,9 @@ pub const MAP_HUGETLB: ::c_int = 0x040000;
 
 pub const EFD_NONBLOCK: ::c_int = 0x800;
 
+pub const F_RDLCK: ::c_int = 0;
+pub const F_WRLCK: ::c_int = 1;
+pub const F_UNLCK: ::c_int = 2;
 pub const F_GETLK: ::c_int = 5;
 pub const F_GETOWN: ::c_int = 9;
 pub const F_SETOWN: ::c_int = 8;