Simplify the Makefile and avoid needing to specify each object file.

Simplify the Makefile and avoid needing to specify each object file.

Instead of specifying every object file, use make's magic to generate
it.
This will generate less conflicts in team branches when a new file is
added in trunk.

(closes issue #15226)
Reported by: eliel
Patches:
      makefile uploaded by eliel (license 64)

      Review: http://reviewboard.asterisk.org/r/269/

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@198139 65c4cc65-6c06-0410-ace0-fbb531ad65f3