Copied from Asterisk, sets some sane values. For instance it enables
IPv6 support.
Also it disables DEBUG. With debug enabled 'pjproject enables "assert"
functions which can cause Asterisk to crash unexpectedly' (quote from
Asterisk wiki). This probably fixes issue #140.
With this config_site.h in place the libsrtp dep can be dropped from
select sub packages.
Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>