Move system_program out of src/

sdk/src/system_program.rs

@@ -0,0 +1,11 @@
+use pubkey::Pubkey;
+
+pub const SYSTEM_PROGRAM_ID: [u8; 32] = [0u8; 32];
+
+pub fn id() -> Pubkey {
+    Pubkey::new(&SYSTEM_PROGRAM_ID)
+}
+
+pub fn check_id(program_id: &Pubkey) -> bool {
+    program_id.as_ref() == SYSTEM_PROGRAM_ID
+}