[package] avahi: Makefile fix to honor configuration changes

[package] avahi: Makefile fix to honor configuration changes

his patch is to fix a long-standing problem with avahi builds:
if you change the configuration, sometimes the relevant packages are not
correctly rebuilt; see, for example, ticket #11110.

Background: avahi can be built in two modes: with or without D-BUS support.
If you switch builds from one mode to the other and then back again, the
packages will not
always be rebuilt as required. For example, if you choose to build avahi (1)
without D-BUS support,
then (2) with D-BUS support and then (3) without D-BUS support, the packages
will not
be rebuilt the third time, and you'll be left with the packages
from the second build -- packages that require D-BUS support.

The patch works by deleting the ".build" file belonging to the mode not
currently chosen, so
that if that mode is chosen again in the future, its packages will always be
rebuilt.

A few small corrections to the explanatory text are included.

Signed-off-by <mikebrady@eircom.net>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@33472 3c298f89-4303-0410-b956-a3cf2f4a3e73