Fix bench build

-Add pos/staker.h to pos/staker.cpp
-Add staker.cpp to Makefile.am

Author: wagerr-builder

src/Makefile.am

@@ -489,6 +489,7 @@ libbitcoin_server_a_SOURCES = \
   pos/checks.cpp \
   pos/kernel.cpp \
   pos/rewards.cpp \
+  pos/staker.cpp \
   pos/stakeinput.cpp \
   pow.cpp \
   rest.cpp \

src/pos/staker.cpp

@@ -6,7 +6,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include "staker.h"
+#include "pos/staker.h"
 
 #include "chain.h"
 #include "chainparams.h"