BUG/MEDIUM: buffer: one byte miss in buffer free space check

Space is not avalaible only if the end of the data inserted
is strictly greater than the end of buffer. If these two value
are equal, the space is avamaible.
diff --git a/src/buffer.c b/src/buffer.c
index e156991..3c7f6cc 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -75,7 +75,7 @@
 
 	delta = len - (end - pos);
 
-	if (bi_end(b) + delta >= b->data + b->size)
+	if (bi_end(b) + delta > b->data + b->size)
 		return 0;  /* no space left */
 
 	if (buffer_not_empty(b) &&