Allow mining RPCs with --disable-wallet

The following mining-related RPC calls don't use the wallet:

- getnetworkhashps
- getmininginfo
- getblocktemplate
- submitblock

Enable them when compiling with --disable-wallet.

src/Makefile.am

@@ -48,9 +48,11 @@ libbitcoin_server_a_SOURCES = \
   keystore.cpp \
   leveldbwrapper.cpp \
   main.cpp \
+  miner.cpp \
   net.cpp \
   noui.cpp \
   rpcblockchain.cpp \
+  rpcmining.cpp \
   rpcnet.cpp \
   rpcrawtransaction.cpp \
   txdb.cpp \
@@ -61,9 +63,7 @@ libbitcoin_server_a_SOURCES = \
 libbitcoin_wallet_a_SOURCES = \
   db.cpp \
   crypter.cpp \
-  miner.cpp \
   rpcdump.cpp \
-  rpcmining.cpp \
   rpcwallet.cpp \
   wallet.cpp \
   walletdb.cpp \