latest Windows build

[Dirk Hohndel]

I now have a Qt 5.11.2 test build for Windows, but at least when I test it
in a VM I run into a rather weird problem. The map doesn't load with the
error 

Cannot load library C:\Program Files (x86)\Subsurface\qml\QtPositioning\declarative_positioning.dll:
the specified module could not be found.

Except exactly that file is indeed there... I see no reason why loading
this DLL should fail (but I may be missing something - definitely not a
Windows expert). If I replace this dll with one from an earlier version I
get a Qt version mismatch error, so the path is indeed correct.

The other thing that I cannot test is whether the experimental BLE support
for Windows is working with this binary (because I don't have a physical
Windows machine with me, nor did I bring a BLE dive computer). I'd
appreciate if someone with a Shearwater Perdix AI, an EON Steel or one of
the other BLE dive computers we support could test this on Windows 10.

The binary is here:

http://subsurface-divelog.org/downloads/test/subsurface-4.8.3-338-gcb89ee49a3cf.exe

Thanks

/D