ThreadData.cpp - thread control class to use in Client
thd.cpp - thread control class to use in Server
To avoid making global visibility of a lot of THD_* ISC_event and so functions in libfbclient.so
(Can be breakable but needed)
Change to --with-sfio=path_to_sfio defaulting to no and substitute values
in to makefiles.
This allows Classic to be built and run without sfio using standard Solaris
stdio while problems between sfio, ib_stdio etc and C++ are sorted out for
superserver.