Merge InstructionError and ProgramError

From the user's perspective, it's just an instruction error.
For program-specific errors, we still have
InstructionError::CustomError.

programs/vote/src/lib.rs

@@ -4,9 +4,9 @@
 use bincode::deserialize;
 use log::*;
 use solana_sdk::account::KeyedAccount;
-use solana_sdk::native_program::ProgramError;
 use solana_sdk::pubkey::Pubkey;
 use solana_sdk::solana_entrypoint;
+use solana_sdk::transaction::InstructionError;
 use solana_vote_api::vote_instruction::VoteInstruction;
 use solana_vote_api::vote_state;
 
@@ -16,13 +16,13 @@ fn entrypoint(
     keyed_accounts: &mut [KeyedAccount],
     data: &[u8],
     _tick_height: u64,
-) -> Result<(), ProgramError> {
+) -> Result<(), InstructionError> {
     solana_logger::setup();
 
     trace!("process_instruction: {:?}", data);
     trace!("keyed_accounts: {:?}", keyed_accounts);
 
-    match deserialize(data).map_err(|_| ProgramError::InvalidInstructionData)? {
+    match deserialize(data).map_err(|_| InstructionError::InvalidInstructionData)? {
         VoteInstruction::InitializeAccount => vote_state::initialize_account(keyed_accounts),
         VoteInstruction::DelegateStake(delegate_id) => {
             vote_state::delegate_stake(keyed_accounts, &delegate_id)

programs/vote/tests/vote.rs

@@ -1,7 +1,6 @@
 use solana_runtime::bank::{Bank, Result};
 use solana_sdk::genesis_block::GenesisBlock;
 use solana_sdk::hash::hash;
-use solana_sdk::native_program::ProgramError;
 use solana_sdk::pubkey::Pubkey;
 use solana_sdk::signature::{Keypair, KeypairUtil};
 use solana_sdk::system_instruction::SystemInstruction;
@@ -134,7 +133,7 @@ fn test_vote_via_bank_with_no_signature() {
         result,
         Err(TransactionError::InstructionError(
             1,
-            InstructionError::ProgramError(ProgramError::InvalidArgument)
+            InstructionError::InvalidArgument
         ))
     );
 }