Fix some potential deadlocks and H.264 video decode error when seeking

[thesword53]

This commit fixes 2 possible deadlocks:

• When a decode error occurs, the surface condition should be signaled otherwise decoding will hang as in Decode error when seeking in H.264 videos #343
• deleteAllObjects should delete all objects not only context objects. I also removed deleteObject because it also calls pthread_mutex_lock(&drv->objectCreationMutex);, so it will cause a deadlock.

[thesword53]

I added a commit to fix #343. In nvCreateContext, I set surfaceCount to 32 if num_render_targets as video players can create surfaces with vaCreateSurfaces/ vaCreateSurfaces2, after calling vaCreateContext.

[elFarto]

Thanks for the effort! A couple of comments:

• The objectCreationMutex lock is created as a recursive lock, so it can be taken repeatedly without issues.
• I'm not sure I like that those macros have been removed for the deleteAllObjects. I can see why you needed to do it, but it doesn't feel right to have all that array manipulation there. I think we need a new method in list.c call something like clear_array that frees all elements, NULLs out the element, and sets the list size to 0. That leaves deleteAllObjects just freeing o->obj.

[thesword53]

Thanks for the effort! A couple of comments:

* The `objectCreationMutex` lock is created as a recursive lock, so it can be taken repeatedly without issues.

* I'm not sure I like that those macros have been removed for the `deleteAllObjects`. I can see why you needed to do it, but it doesn't feel right to have all that array manipulation there. I think we need a new method in `list.c` call something like `clear_array` that frees all elements, NULLs out the element, and sets the list size to 0. That leaves `deleteAllObjects` just freeing o->obj.

I reverted changes in deleteAllObjects