freeswitch: revisit build setup

freeswitch: revisit build setup

1. Upstream fixed the parallel build issue in
   90ea0b7a1fdd7d8c5adaac87d74ed1c3c74086d0, so no need to force it off
   anymore.

2. The same sed script for uncommenting modules in modules.conf is used
   multiple times. This commit puts the script into a define that can be
   reused.

3. Some ifdefs removed. They only clutter up the Makefile. The sed
   script can run a few extra times, it does not matter.

4. Add a few extra dependencies that came to light.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>