Revert keccak change, get test_opcode to run

src/logic/block_ops.nim

@@ -1,5 +1,5 @@
 import
-  ../constants, ../errors, ../computation, ../vm_state, ../types, .. / vm / [stack], ttmath
+  ../constants, ../errors, ../computation, ../vm_state, ../types, .. / vm / [stack]
 
 {.this: computation.}
 {.experimental.}
@@ -19,6 +19,7 @@ proc timestamp*(computation) =
   # TODO: EthTime is an alias of Time, which is a distinct int64 so can't use u256(int64)
   # This may have implications for different platforms.
   stack.push(vmState.timestamp.uint64.u256) 
+  stack.push(vmState.timestamp.u256)
 
 proc number*(computation) =
   stack.push(vmState.blockNumber)

src/utils/keccak.nim

@@ -1,18 +1,8 @@
 import
-  nimcrypto, strutils
+  keccak_tiny, strutils
 
-#[
 template keccak*(value: string): string =
   $keccak_256(value)
 
 template keccak*(value: cstring): string =
   ($value).keccak
-]#
-
-proc keccak*(value: string): string =
-  # TODO: Urgent - check this is doing the same thing as above
-  var k = sha3_256()
-  k.init
-  k.update(cast[ptr uint8](value[0].unsafeaddr), value.len.uint)
-  result = $finish(k)
-