C/LLVM backend: Emit member procs/vars just like any other globals

- static member var declarations will now really be emitted,
  they previously weren't (despite 9569cbba) because the IsAccessed stat
  wasn't set yet when the hEmitStructs() was called, because that stat
  currently is set during astLoadVAR() only. Now it works because
  hEmitDecls() handles the emitting, and that's called at the end of
  emitting the module, when all IsAccessed stats have been set as needed.

- member proc declarations will now only be emitted when they were actually
  called, like other procs, respecting the IsAccessed stat
tests: Compile in new varargs test case under -gen gas only

(-gen gcc doesn't currently allow va_*())