[OpenSIPS-Devel] [OpenSIPS/opensips] eec31b: Makefile.defs: Improve docbook.xsl detection

[Liviu Chircu]

  Branch: refs/heads/master
  Home:   https://github.com/OpenSIPS/opensips
  Commit: eec31bd98ec1a8d398a963697687bf2555cf62b8
      https://github.com/OpenSIPS/opensips/commit/eec31bd98ec1a8d398a963697687bf2555cf62b8
  Author: Liviu Chircu <liviu at opensips.org>
  Date:   2019-05-29 (Wed, 29 May 2019)

  Changed paths:
    M Makefile.defs

  Log Message:
  -----------
  Makefile.defs: Improve docbook.xsl detection

An adaptation of commit faec7ebc9473 which also helps preserve the
previous behavior.