cpp: Fix implementations of "list<bool>"

cpp: Fix implementations of "list<bool>"

TProtocol::readBool expects a "bool&" as its argument, but "list<bool>"
is implemented as "vector<bool>", which is a specialization of vector
that uses a custom structure as its reference type.  Therefore, we need
to overload TProtocol::readBool for std::vector<bool>::reference.
This function is provided as a non-virtual for efficiency since it is
highly unlikely that any subclass will want to override it.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@743112 13f79535-47bb-0310-9956-ffa450edef68