Remove unsafe "__as_link()" cast member function.
Remove unsafe "__as_link()" cast member function.

"__as_link()" can only be used safely on "__list_node" objects. This patch
moves the "__as_link()" member function from "__list_node_base" to "__list_node"
so it cannot be used incorrectly.

Unsafe downcasts now use a non-member function so we don't defer the type-punned
pointer.


git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@256727 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx