- fix bug in pfm_unload(), not allowed when not on correct CPU for
          system-wide
        - some perf/cleanup in overflow handler
        - fix reset_pmds to be on a per PMD basis on counter overflow rather
          than global
        - remove timing debug code on messages
        - no kernel info leak on PFM_END_MSG
        - remove double-store on reg_flags for pfm_write_pmcs, pfm_write_pmds
        - on restart reset_pmds is 0 by default
        - cleanup useless macros
        - cleanup some debug prints
        - added ability to remove debug code
        - streamlined sys_perfmonctl(), pfm_read_pmds(), pfm_write_*()
        - added current->tgid to default format sample header by using one
          reserved field