rb: add a first version of the library

first working version of the library. the binary stuff is included.
we can write to and read from a ring buffer.
rb: add ascii support

in order to be able to deal with strings (i.e null terminated), we
provide a new set of functions

rb_puts
rb_printf / rb_vprintf
rb_gets / rb_gets2
rb: allow to remove data from a ring buffer

we provide two new ways to remove data from a ring_buffer

rb_remove(rb, n)
or
rb_get(rb, NULL, n)

closes #2
rb: improve the performance of rb_put

when we call rb_put with a size greater than the size of the ring buffer
itself, we used to copy in a loop, overriding our new written datas.

it was very inefficient so we avoid these computations

closes #1
rb: use the rb_remove function where it needs to be
rb: fix a dangerous comment

we provided an example to show how to use rb_gets2 but did not NULL-terminate
our array of delimiters.
rb: t_rb has been renamed to rb_t

t_rb will be kept in the source files for backward compatibility.
However, it will not have to be used anymore.
Create LICENSE
rb: add a header mentionning the GPL license in every source file
rb: fix compilation issue

rb.h uses an inline definition of rb_remove which uses NULL.
since the standard declaration of NULL can be found in stdlib.h, we
need to include it.
rb: use the autotools to generate the library

the library is not built using the autotools.

the advantages of this improvement are:

* we can do a make install / make uninstall / make dist / and so on
* the library is not (unless specified) built as a shared and static
  library
* some portability issues will be easier to fix.
rb: happy new year

Copyright updated in every source file