Some fix in the ELF parser

Thanks you for your answer, and sorry for the inconvenient. I understand better now, how pull request works.

I take care your remarks, and I rewriten the fully patch in a new branch called 'elf-parser'

In this patch, I also corrected an 'out of bound' bug in r_buf_fcpy_at.

If i'm doing something wrong now, tell me !

Best regards,
-TOSH-
What about using `calloc` instead?