Fix the spelling of length. (#14)

src/encode.c

@@ -339,7 +339,7 @@ static uint32_t assess_splitting_option(struct aec_stream *strm)
        increases, then the minimum will be found with smaller k.
 
        For increasing k we know that we will gain block_size bits in
-       length through the larger binary part. If the FS lenth is less
+       length through the larger binary part. If the FS length is less
        than the block size then a reduced FS part can't compensate the
        larger binary part. So we know that the CDS for k+1 will be
        larger than for k without actually computing the length. An

tests/check_aec.h

@@ -12,7 +12,7 @@ struct test_state {
     unsigned char *ubuf;
     unsigned char *cbuf;
     unsigned char *obuf;
-    size_t ibuf_len; /* input buffer legth may be shorter than buf_len */
+    size_t ibuf_len; /* input buffer length may be shorter than buf_len */
     size_t buf_len;
     size_t cbuf_len;
     long long int xmax;