Unexpected warning on OSX with gcc7

Not major problem but look like some missing include or invalid build configuration

ecl/src/c/ffi.d:903:28: warning: implicit declaration of function 'ffi_closure_alloc' [-Wimplicit-function-declaration]
     ffi_closure *closure = ffi_closure_alloc(sizeof(ffi_closure), &executable_region);
                            ^~~~~~~~~~~~~~~~~
ecl/src/c/ffi.d:903:28: warning: initialization makes pointer from integer without a cast [-Wint-conversion]
ecl/src/c/ffi.d:917:18: warning: implicit declaration of function 'ffi_prep_closure_loc'; did you mean 'ffi_prep_closure'? [-Wimplicit-function-declaration]
     int status = ffi_prep_closure_loc(closure, cif, callback_executor,
                  ^~~~~~~~~~~~~~~~~~~~
                  ffi_prep_closure

Please note the this is build that contain already merge request !95 (merged)