python: multi_usrp: Let get_tree() return a raw pointer

This changes the Python version of MultiUSRP.get_tree() such that it
returns a raw pointer to the tree instead of returning the sptr.
This fixes an issue where calling get_tree() will reliably cause
a segfault during garbage collection, at least on some USRPs.

The downside of this approach is that storing the return value from
get_tree() can produce a dangling pointer when the underlying object is
destroyed. It's still better than segfaults, and the recommended way to
use get_tree() anyway is not to store the return value (unless it's in
a local scope), but tack on property tree methods to get_tree() itself.
Examples:
>>> usrp = uhd.usrp.MultiUSRP('...')
>>> usrp.get_tree().exists('/path/to/prop') # This is fine

This change has no noticable API changes.

0 files changed, 0 insertions, 0 deletions