install_prereq: Update FreeBSD libraries.

Because the code review system Gerrit creates merge conflicts even when one line
apart another change happened, the previous update to the FreeBSD libraries had
to be rebased via Git. Because of a break for training of the original
contributor, this rebase was done by another contributor and the variant for
Asterisk 13 was cherry-picked to all branches. By this, dependencies for new
features added in newer Asterisk version got lost. This can be seen, when not
the original path set but a previous patch set is compared.

This change here fixes this by adding those (optional) dependencies for
Asterisk 15 and newer (again).

ASTERISK-27686

Change-Id: I6638a3d0dc37ad4ff5f94be15463e3dd8a2bfe74

contrib/scripts/install_prereq

@@ -76,6 +76,7 @@ PACKAGES_FBSD="$PACKAGES_FBSD postgresql10-client unixODBC libltdl neon gmime26
 PACKAGES_FBSD="$PACKAGES_FBSD mysql57-client radcli freetds"
 PACKAGES_FBSD="$PACKAGES_FBSD net-snmp iksemel corosync newt popt libical spandsp"
 PACKAGES_FBSD="$PACKAGES_FBSD cclient libbfd libsrtp gsm libilbc doxygen graphviz libzip openldap-client libhoard"
+PACKAGES_FBSD="$PACKAGES_FBSD codec2 fftw3 libsndfile unbound"
 # Asterisk: for the unpackaged below:
 PACKAGES_FBSD="$PACKAGES_FBSD wget subversion"
 # Asterisk: for ./configure --with-pjproject-bundled: