Added no entrypoint feature (#41)

Co-authored-by: Dafydd Durairaj <dafydd.durairaj@gmail.com>

dex/Cargo.toml

@@ -13,6 +13,7 @@ client = ["solana-sdk/default", "spl-token/default"]
 fuzz = ["arbitrary", "solana-sdk/curve25519-dalek"]
 test = ["solana-sdk/default"]
 default = []
+no-entrypoint = []
 
 [dependencies]
 solana-sdk = { version = "=1.3.14", default-features = false }

dex/src/lib.rs

@@ -18,6 +18,7 @@ use solana_sdk::{
 };
 
 #[cfg(feature = "program")]
+#[cfg(not(feature = "no-entrypoint"))]
 entrypoint_deprecated!(process_instruction);
 #[cfg(feature = "program")]
 fn process_instruction(