Add additional asserts() to ensure certain operations are not performed when the...

Add additional asserts() to ensure certain operations are not performed when the scheduler is suspended.
Change the xBlockTime variables in event_groups.c/h to xTicksToWait to match the naming in other core FreeRTOS files.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2116 1d2547de-c912-0410-9cb9-b8ca96c0e9e2