dbx_tree merged with the cache management code

git-svn-id: http://svn.miranda-ng.org/main/trunk@4408 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c
dbx_mmap: protocol cache is used more intensively 

git-svn-id: http://svn.miranda-ng.org/main/trunk@4409 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c
write locks for MDatabaseCache

git-svn-id: http://svn.miranda-ng.org/main/trunk@4410 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c