File access properties

[sreekants]

I was looking for a way to access the last access, creation and read time for a file.
It would be useful to do a few things:

• Expose the SdFile reference in the File object to access the more low-level features available in SdFile
• Provide a feature to inquire time properties of the dir_t structure in a directory. This would allows a stat() like capability.

[GonzalezAnguita]

Hanging from this request. Would be great to have access to the rewind(void) method of the SDFile class in <SDFat.h> to avoid having to close and reopen a file.

My case applies for using an instructions file that must be run in each loop( ) iteration. Loading the whole instructions file into memory is not feasible because it's too big so the current solution is opening the file and closing it on every loop( ) iteration.

The implementation should be pretty straightforward if I'm correct, adding the following into the SD.cpp file.

    629  void File::rewindDirectory(void) {  
    630    if (isDirectory())
    631      _file->rewind();
    632  }

    633  void File::rewind(void) {  
    634    _file->rewind();
    636  }

I'm not sure if there is an unexpected behavior when resetting the file index