Merge remote-tracking branch 'stefanha/trivial-patches' into staging

Merge remote-tracking branch 'stefanha/trivial-patches' into staging

* stefanha/trivial-patches:
  make: fix clean rule by removing build file in qom/
  configure: Link qga against UST tracing related libraries
  configure: Link QEMU against 'liburcu-bp'
  main-loop: make qemu_event_handle static
  block/curl: Replace usleep by g_usleep
  qtest: Add missing GCC_FMT_ATTR
  w32: Undefine error constants before their redefinition
  configure: fix mingw32 libs_qga typo