[gimp] Fix rle encoding, first byte of run was added to previous non-run.

[Jehan Pagès <jehanp src gnome org>]

commit c3dc3ea59f25de57703390123a14039fb7a2c0eb
Author: HJ Imbens <hj imbens nl>
Date:   Wed Nov 25 09:35:57 2015 +0100

    Fix rle encoding, first byte of run was added to previous non-run.

 app/xcf/xcf-save.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/app/xcf/xcf-save.c b/app/xcf/xcf-save.c
index fd981c0..eeee9e9 100644
--- a/app/xcf/xcf-save.c
+++ b/app/xcf/xcf-save.c
@@ -1654,6 +1654,13 @@ xcf_save_tile_rle (XcfInfo        *info,
                 {
                   const guchar *t;
 
+                  /* if we came here because of a new run, backup one */
+                  if (!((length == 32768) || ((size - length) == 0)))
+                    {
+                      length--;
+                      data -= bpp;
+                    }
+
                   count += length;
                   state = 0;