Move arith_uint256 out of consensus and util

src/Makefile.am

@@ -233,6 +233,7 @@ univalue_libbitcoin_univalue_a_SOURCES = \
 libbitcoin_common_a_CPPFLAGS = $(BITCOIN_INCLUDES)
 libbitcoin_common_a_SOURCES = \
   allocators.cpp \
+  arith_uint256.cpp \
   amount.cpp \
   base58.cpp \
   chainparams.cpp \
@@ -262,7 +263,6 @@ libbitcoin_common_a_SOURCES = \
 # backward-compatibility objects and their sanity checks are linked.
 libbitcoin_util_a_CPPFLAGS = $(BITCOIN_INCLUDES)
 libbitcoin_util_a_SOURCES = \
-  arith_uint256.cpp \
   chainparamsbase.cpp \
   clientversion.cpp \
   compat/glibc_sanity.cpp \
@@ -354,7 +354,6 @@ bitcoin_cli_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 if BUILD_BITCOIN_LIBS
 include_HEADERS = script/bitcoinconsensus.h
 libbitcoinconsensus_la_SOURCES = \
-  arith_uint256.cpp \
   crypto/hmac_sha512.cpp \
   crypto/ripemd160.cpp \
   crypto/sha1.cpp \