Avoid a strict two-phase instatiation error.

svn path=/sandbox/unordered/boost/unordered/; revision=42110
Remove 'local_iterator_base'. It isn't really needed.

svn path=/sandbox/unordered/boost/unordered/; revision=42153
Add a helper function for creating null pointers.

svn path=/sandbox/unordered/boost/unordered/; revision=42155
Check that I'm using link_ptr & bucket_ptr correctly (they should be distinct
types with an explicit conversion from bucket_ptr to link_ptr).

svn path=/sandbox/unordered/boost/unordered/; revision=42156
Tweak the function specifiers a tad bit.

svn path=/sandbox/unordered/boost/unordered/; revision=42157
No need to create a node_constructor for every iteration.

svn path=/sandbox/unordered/boost/unordered/; revision=42158
Pull another node_constructor out of a loop.

svn path=/sandbox/unordered/boost/unordered/; revision=42159
Remove unrequired include.

svn path=/sandbox/unordered/libs/unordered/; revision=42172