THRIFT-2417: Make union types partial classes

Patch by Jake Luciani, Reviewed by Jake Farrell
THRIFT-2415 Named pipes server performance & message mode

Patch: Jens Geyer
THRIFT-2418 Go handler function panics on internal error

Patch: Frank Schroeder
THRIFT-2419 golang - Fix fmt.Errorf in generated code

Patch: Chris Bannister
THRIFT-2420 Go argument parser for methods without arguments does not skip fields

Patch: Frank Schroeder & Jens Geyer
THRIFT-2425 PHP: Server-side support for Multiplexing Services

Patch: Aldo Armiento