The boolean operator || requires an evaluation of both expressions.
If the expressions evaluates pointers, then care must be taken that
both expressions have valid pointer. In this case it cannot be guaranteed,
thus splitting the check is needed.

The location of an object in the heap was wrongly determined, by applying the HEAP_ID_MASK to the object id. Instead the heap->id_offset should have been substracted from the object id. The object id is created by using the i-th position plus heap->id_offset.

The boolean operator || requires an evaluation of both expressions.
If the expressions evaluates pointers, then care must be taken that
both expressions have valid pointer. In this case it cannot be guaranteed,
thus splitting the check is needed.

Remove association buffers if adding did not work properly.

Instead of aborting on an empty buffer we just continue, since the
buffer would be freed anyway on the next line. This patch makes the
function more tolerant.

The original install rule would fail if the link already existed.
Now installing succeeds if the destination was already there, it will
be overwritten with the new file.

The extern keyword is needed for instructing the linker to resolve
hw_image_hooks_glx, which is declared in another object. Failing to
do so results in an assert later on when using subpictures.