Make description of the lss16 format match reality

The comment in ppmtolss16 is perhaps how the lss16 format *should*
work, but not actually how it *does* work.

diff --git a/ppmtolss16 b/ppmtolss16
index a63e0a2..5af9083 100755 (executable)
--- a/ppmtolss16
+++ b/ppmtolss16
@@ -25,9 +25,9 @@
 ##
 ## N   ... if N is != previous pixel, one pixel of color N
 ## ... otherwise run sequence follows ...
-## M    ... if M > 0 then run length is M+1
+## M    ... if M > 0 then run length is M
 ## ... otherwise run sequence is encoded in two nybbles,
-##     littleendian, +17
+##     littleendian, +16
 ##
 ## The nybble sequences are on a per-row basis; runs may not extend
 ## across rows and odd-nybble rows are zero-padded.