int64_t incompatible with enif_get_int64 warning on OS X

[acautin]

Ref: #79 (comment)

cd c_src/odpi && make
make[1]: Nothing to be done for `all'.
gcc -o priv/dpi_nif.so -Ic_src -I"/Users/agustin/kerl/20.2/erts-9.2/include" -I"c_src/odpi/include" -O2 -ggdb -Wall -fPIC -std=c11 -dynamiclib  c_src/dpiConn_nif.c c_src/dpiContext_nif.c c_src/dpiData_nif.c c_src/dpiQueryInfo_nif.c c_src/dpiStmt_nif.c c_src/dpiVar_nif.c c_src/dpi_nif.c -Lc_src/odpi/lib -shared -lodpic -flat_namespace -undefined suppress
c_src/dpiData_nif.c:187:39: warning: incompatible pointer types passing 'int64_t *' (aka 'long long *') to parameter of type 'long *' [-Wincompatible-pointer-types]
    if (!enif_get_int64(env, argv[1], &amount))
                                      ^~~~~~~
/Users/agustin/kerl/20.2/erts-9.2/include/erl_nif_api_funcs.h:104:79: note: passing argument to parameter 'ip' here
ERL_NIF_API_FUNC_DECL(int,enif_get_long,(ErlNifEnv*, ERL_NIF_TERM term, long* ip));
                                                                              ^
1 warning generated.