Version 0.9.2

This release addresses two somewhat exotic ways self_cell could be used in an
unsound fashion to cause UB. See issues #17 and #18. Thanks @steffahn for
reporting and helping to fix these issues.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "self_cell"
-version = "0.9.1"
+version = "0.9.2"
 authors = ["Lukas Bergdoll <[email protected]>"]
 edition = "2018"
 license = "Apache-2.0"