abci: Fix documentation regarding CheckTx type update (#3789)

* Update ABCI docs to reflect latest changes on PR #3744

* Add note about new Type parameter for CheckTx

docs/spec/abci/abci.md

@@ -297,11 +297,9 @@ Commit are included in the header of the next block.
 - **Request**:
   - `Tx ([]byte)`: The request transaction bytes
   - `Type (CheckTxType)`: What type of `CheckTx` request is this? At present,
-    there are two possible values: `CheckTx_Unchecked` (the default, which says
-    that a full check is required), and `CheckTx_Checked` (when the mempool is
+    there are two possible values: `CheckTx_New` (the default, which says
+    that a full check is required), and `CheckTx_Recheck` (when the mempool is
     initiating a normal recheck of a transaction).
-  - `AdditionalData ([]byte)`: Reserved for future use. See
-    [here](https://github.com/tendermint/tendermint/issues/2127#issuecomment-456661420).
 - **Response**:
   - `Code (uint32)`: Response code
   - `Data ([]byte)`: Result bytes, if any.

docs/spec/abci/apps.md

@@ -65,7 +65,10 @@ begin.
 After `Commit`, CheckTx is run again on all transactions that remain in the
 node's local mempool after filtering those included in the block. To prevent the
 mempool from rechecking all transactions every time a block is committed, set
-the configuration option `mempool.recheck=false`.
+the configuration option `mempool.recheck=false`. As of Tendermint v0.32.1,
+an additional `Type` parameter is made available to the CheckTx function that 
+indicates whether an incoming transaction is new (`CheckTxType_New`), or a
+recheck (`CheckTxType_Recheck`).
 
 Finally, the mempool will unlock and new transactions can be processed through CheckTx again.