Continue work on STM32L demo.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2111 1d2547de-c912-0410-9cb9-b8ca96c0e9e2
Add event_groups.c and associated functions in other core files.
Added xTimerPendCallbackFromISR() to provide a centralised deferred interrupt handling mechanism.
Add xPortGetLowestEverFreeHeapSize() to heap_4.c.


git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2112 1d2547de-c912-0410-9cb9-b8ca96c0e9e2
Add event groups test/demo tasks.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2113 1d2547de-c912-0410-9cb9-b8ca96c0e9e2
Merge remote-tracking branch 'trunk'