message: remove utf8 api
diff: #include <fc/crypto/sha256.hpp>
  #include <fc/crypto/sha1.hpp>
  #include <fc/io/raw.hpp>
  -#include <fc/utf8.hpp>
  #include <softfloat.hpp>
  #include <boost/asio.hpp>
  @@ -784,17 +783,6 @@ class permission_api : public context_aware_api {
  }
  };
  -class string_api : public context_aware_api {
  - public:
  - using context_aware_api::context_aware_api;
  -
  - void assert_is_utf8(array_ptr<const char> str, size_t datalen, null_terminated_ptr msg) {
  - const bool test = fc::is_utf8(std::string( str, datalen ));
  -
  - FC_ASSERT( test, "assertion failed: ${s}", ("s",msg.value) );
  - }
  -};
  -
  class system_api : public context_aware_api {
  public:
  explicit system_api( apply_context& ctx )
  @@ -1552,10 +1540,6 @@ REGISTER_INTRINSICS(permission_api,
  (check_authorization, int(int64_t, int64_t, int, int))
  );
  -REGISTER_INTRINSICS(string_api,
  - (assert_is_utf8, void(int, int, int) )
  -);
  -
  REGISTER_INTRINSICS(system_api,
  (abort, void() )
  (eosio_assert, void(int, int) )
  