use buffered streams to reduce the number of TCP packets used per IPC command from...

use buffered streams to reduce the number of TCP packets used per IPC command from up to 7 to 1 for reasonably sized payloads, this dramatically (by 150 times for the IPC benchmark on a LAN) increases performance; also centralize all the streams used in a single wxIPCSocketStreams class and allocate only it on the heap instead of doing it for all of the streams

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56584 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775