Patches from fedora and fixes for LMDB backend

[Ignacio Casal <ignacio.casal@xxxxxxxxxxxxxxxxx>]

Hey guys,

I would like to highlight a couple of more patches coming from fedora:
https://github.com/nice-software/cyrus-sasl/commit/49be817dd38cbbdcd7938ef61ef7c684a2a62460
https://github.com/nice-software/cyrus-sasl/commit/835ba08e68bb1e1cec8dae155b457dd553e762fb

Also, I made some fixes to the mdb backend to rename it to lmdb and to use the renamed library lmdb instead of mdb (since it seems to have changed upstream)

See: https://github.com/nice-software/cyrus-sasl/commits/wip/lmdb

As a plus I also modified the nmake stuff to allow to build the lmdb backend instead of libdb. This is still not quite well tested but some comment are welcomed.
https://github.com/nice-software/cyrus-sasl/commit/d0cc4dfe20e71aef853a7f73f6228d1a268b2845

From another side, the lmdb maintainer is not interested on supporting MSVC builds, even though I made a fork in case somebody wants to give it a try:
https://github.com/nice-software/lmdb/tree/wip/msvc

At this point a question arises, should we support a backend that we cannot build on the platforms supported by cyrus-sasl? That is, should we drop lmdb since the maintainer is not interested on it? Also we have the code that is not building at all without the patches I pointed out.

Regards.

--

Ignacio Casal Quinteiro