windows-more-cleanups-20060201

windows-more-cleanups-20060201

* remove all references to 'dead_vcp'; cleanup smb_vc_t's as soon as
  we know they are dead

* add mx holds across the cm_cell_t updates

* add cm_FindSCacheParent() and remove duplicate code elsewhere

* add mx holds across scp->flags updates

* add cm_CleanFile()

* clear CM_SCACHEFLAG_CALLBACK when discarding callbacks

* fix smb fid wrapping.  wrap at 0xFFFF instead of 0 because 0xFFFF
  is -1 which is INVALID_HANDLE

* add missing mx holds around vcp->flags updates