BuildSystem: Enable autotools in FreeBSD.

In the current versions of FreeBSD, the apps of GNU autotools do not need to
be called with a version anymore. The latest version can be invoked directly.
Additionally, the script ./bootstrap.sh asked for autoconf 2.62 and
automake 1.9, versions which are not available as port anymore.

ASTERISK-27637

Change-Id: Id7b94b80e78cc943a40ba79b697e3f70019820a7

bootstrap.sh

@@ -13,9 +13,9 @@ check_for_app() {
 # On Linux, environment variables tell which one to use.
 
 case `uname -sr` in
-	'FreeBSD 4'*)	# FreeBSD 4.x has a different naming
-		MY_AC_VER=259
-		MY_AM_VER=19
+	FreeBSD*)
+		MY_AC_VER=
+		MY_AM_VER=
 		;;
 	OpenBSD*)
 		export AUTOCONF_VERSION=2.63