(ITS#8324) LMDB - grow file incrementally on Windows

[hyc@openldap.org]

Full_Name: Howard Chu
Version: LMDB 0.9.17
OS: Win32 x64
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (78.155.236.172)
Submitted by: hyc


Currently LMDB uses the WIN32 API to setup the memory-mapped DB file, which
requires that the file size is equal to the map size. If we use the native NT
API instead it's possible to grow the file incrementally, which will reduce the
number of complaints we get from Windows users who think their disk space is
getting eaten up for no reason.

There is probably a performance reduction from taking this approach, but I
haven't benchmarked it and have no plans to. I frankly don't care and no one is
paying me to care.