Fix: Possible buffer overflows in strncat() usage

Fix: Possible buffer overflows in strncat() usage

When using strncat, the size_t n argument must indicate the left over
space remaining in the buffer, *not* the total buffer size. Also, proper
care must be taken for the case where src contains n or more bytes and
thus allow space for the null terminating byte appended to dest (e.g.
strncat() will write n+1 bytes).

Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>