Restarting event log results in invalid output

Currently if one calls endEventLogging(), followed by beginEventLogging(), the eventlog that results has block markers before the header, rendering the output unreadable to ghc-events. The problem is that endEventLogging() calls printAndClearEventsBuf(&eventBuf), which posts a marker after flushing the buffer. postHeaderEvents() then fails to clear this marker before posting the header.

The solution seems clear: call resetEventsBuf() in either endEventLogging() or postHeaderEvents().