BuildSystem: Enable autotools in Solaris 11.

Because this was the last operating system which required a special case, a
version appended to the autotools, the whole version stuff is removed by this
change. This simplifies the script ./bootstrap.sh. Hopefully, this gives even
broader platform compatibility.

ASTERISK-27929
ASTERISK-27926

Change-Id: Id4cf433a1a7fa861d0210e1a2e16ca592b49fd5a