Add MS_NOSYMFOLLOW flag

MS_NOSYMFOLLOW (since Linux 5.10) disallows automatic following of symlinks. 

See:
torvalds/linux@dab741e

Author: tedbrandston

src/unix/linux_like/mod.rs

@@ -654,6 +654,7 @@ pub const MS_SYNCHRONOUS: c_ulong = 0x10;
 pub const MS_REMOUNT: c_ulong = 0x20;
 pub const MS_MANDLOCK: c_ulong = 0x40;
 pub const MS_DIRSYNC: c_ulong = 0x80;
+pub const MS_NOSYMFOLLOW: c_ulong = 0x100;
 pub const MS_NOATIME: c_ulong = 0x0400;
 pub const MS_NODIRATIME: c_ulong = 0x0800;
 pub const MS_BIND: c_ulong = 0x1000;