Some code needs to read directly into eina_binbuf to avoid an extra
copy from eina_binbuf_append* variants.
This can be achieved by using eina_binbuf_expand(), which returns a
write-able slice of the spare bytes. Once they are used,
eina_binbuf_use() should be called to increment "buf->len", which is
used by all other binbuf functions such as eina_binbuf_length_get() or
eina_binbuf_append_slice().
It is sometime useful to start from a defined buffer, but to not touch it
until needed. This make life of caller more easier as they don't need to
duplicate the buffer themself as Eina will now take care of that.
Gustavo Sverzut Barbieri
Tom Hacohen
Cedric BAIL
Carsten Haitzler
Vincent Torri