change php namespace in standard.thrift to apache_thrift_type_standard
change php namespace in standard.thrift to apache_thrift_type_standard

Summary: We can't have same php namespace in multiple thrift files when there are constant variables, since php creates namespace_CONSTANTS class for each file. Currently we already use `apache_thrift_type` namespace in type.thrift.

Reviewed By: prasad223

Differential Revision: D38952229

fbshipit-source-id: 736a65bb430cf8a4002e5451d587404d4659cef0

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift