Ruby exception constructor bugfix

Ruby exception constructor bugfix

The Ruby exception constructor is modified to accept 0 arguments, which is
how Thrift library code creates exception objects. Without this fix, Thrift
Ruby clients that receive exception objects crash.

The call to super (resolving to ThriftStruct#initialize) is retained, but
is called with the default value (an empty hash) instead of passing the
message along.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665501 13f79535-47bb-0310-9956-ffa450edef68