Fix: Uninitialized ctf_stream_pos structure in ctf_float_write()

This structure is passed to _ctf_float_copy() which uses the
uninitialized mmap_offset and offset values to read the source
floating point value.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Do not automatically create a new packet when aligning ctf_stream_pos

ctf_align_pos() will call ctf_packet_seek() and start a new packet if
the alignment cannot be achieved in the current packet. This change
performs the ctf_pos_access_ok() check before aligning. EFAULT will
be returned to the caller, thus giving him a chance to either resize
the current packet or to create a new one.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Add public CTF Writer API headers

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Add CTF Writer implementation

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add a CTF Writer test

The test will be ran as part of the "tests" test plan.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>