Remove SYS_UMASK.

Now that all POSIX open-related calls go through relibc, this value can
be downgraded to a (process-local) global variable in userspace.

src/call.rs

@@ -292,11 +292,6 @@ pub fn setreuid(ruid: usize, euid: usize) -> Result<usize> {
     unsafe { syscall2(SYS_SETREUID, ruid, euid) }
 }
 
-/// Set the file mode creation mask
-pub fn umask(mask: usize) -> Result<usize> {
-    unsafe { syscall1(SYS_UMASK, mask) }
-}
-
 /// Remove a file
 pub fn unlink<T: AsRef<str>>(path: T) -> Result<usize> {
     unsafe {

src/number.rs

@@ -88,6 +88,5 @@ pub const SYS_SETPGID: usize = 57;
 pub const SYS_SETREGID: usize = 204;
 pub const SYS_SETRENS: usize = 952;
 pub const SYS_SETREUID: usize = 203;
-pub const SYS_UMASK: usize = 60;
 pub const SYS_WAITPID: usize = 7;
 pub const SYS_YIELD: usize = 158;