Import Debian changes 2.5.3+dfsg-4

blt (2.5.3+dfsg-4) unstable; urgency=medium

  * Rebuild to restore binary compatibility with the current Tcl/Tk 8.6
    (closes: #888818).
  * Bump the debhelper compatibility level to 10.
  * Remove usage of autotools-dev and dh_autoreconf since they aren't
    necessary for debhelper compatibility level 10.
  * Bump the standards version to 4.1.3.