extract some basic code from libcryptonote_core into libcryptonote_basic

src/ringct/CMakeLists.txt

@@ -49,5 +49,6 @@ target_link_libraries(ringct
   PUBLIC
     common
     crypto
+    cryptonote_basic
   PRIVATE
     ${EXTRA_LIBRARIES})

src/ringct/rctSigs.cpp

@@ -34,7 +34,7 @@
 #include "common/thread_group.h"
 #include "common/util.h"
 #include "rctSigs.h"
-#include "cryptonote_core/cryptonote_format_utils.h"
+#include "cryptonote_basic/cryptonote_format_utils.h"
 
 using namespace crypto;
 using namespace std;