Consistently use the function name CreateCheckPoint in code and comments.

Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACVZmKsvDjtd45+9oTcnjUJtC4LF2BYK8TpWT1f=NjJX3w@mail.gmail.com

src/backend/storage/buffer/bufmgr.c

@@ -3907,7 +3907,7 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
 			 * never gets written, so crash recovery will fix.
 			 *
 			 * It's possible we may enter here without an xid, so it is
-			 * essential that CreateCheckpoint waits for virtual transactions
+			 * essential that CreateCheckPoint waits for virtual transactions
 			 * rather than full transactionids.
 			 */
 			MyProc->delayChkpt = delayChkpt = true;

src/backend/storage/ipc/standby.c

@@ -1182,7 +1182,7 @@ standby_redo(XLogReaderState *record)
  * starting to accumulate changes at a point just prior to when we derive
  * the snapshot on the primary, then ignore duplicates when we later apply
  * the snapshot from the running xacts record. This is implemented during
- * CreateCheckpoint() where we use the logical checkpoint location as
+ * CreateCheckPoint() where we use the logical checkpoint location as
  * our starting point and then write the running xacts record immediately
  * before writing the main checkpoint WAL record. Since we always start
  * up from a checkpoint and are immediately at our starting point, we