erlang: Add a state-propagation-testing transport

erlang: Add a state-propagation-testing transport

Add a transport implementation that forwards all read and write (and
flush and close) requests directly to a wrapped transport.  In addition,
it keeps a small amount of state: a version number that is incremented
on each operation and the PID of a process that stores another copy of
the version number.  Every operation compares the version numbers and
increments both.  If some part of the Thrift stack doesn't propagate
state updates properly, the two versions will not match.

Also add some (compiled-off by default) code to thrift_transport to
auto-wrap every transport in a state checker.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@990990 13f79535-47bb-0310-9956-ffa450edef68