In process of module testing event_groups.c.

In process of module testing event_groups.c.
Introduce xPortRunning variable into Win32 simulator port layer.
Add port optimised task selection macro for the GCC Win32 port layer (the MSVC version has had one for a while).
Ensure the event list item value does not get modified by code in tasks.c (priority inheritance, or priority change) when it is in use by the event group implementation.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2137 1d2547de-c912-0410-9cb9-b8ca96c0e9e2