Fix syscall definitions for x86_64-unknown-linux-gnux32.

libc::syscall takes a c_long as in x86_64-unknown-linux-gnu [1], but
c_long is i32 rather than i64 [2].

The syscall numbers include 0x40000000 as an indicator of the ABI [2].

[1]: rust-lang/libc:src/unix/linux_like/linux/mod.rs
[2]: rust-lang/libc:src/unix/linux_like/linux/gnu/b64/x86_64/x32.rs

Author: hvdijk

src/nr.rs

@@ -61,11 +61,16 @@ pub const CAPGET: i32 = 184;
 #[cfg(target_arch = "x86")]
 pub const CAPSET: i32 = 185;
 
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 pub const CAPGET: i64 = 125;
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 pub const CAPSET: i64 = 126;
 
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "32"))]
+pub const CAPGET: i32 = 0x40000000 + 125;
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "32"))]
+pub const CAPSET: i32 = 0x40000000 + 126;
+
 #[cfg(target_arch = "aarch64")]
 pub const CAPGET: i64 = 90;
 #[cfg(target_arch = "aarch64")]