WIP fix

Bug is fixed, but appears to have broken vision underwater. Notes:

+ basically fixed by darkening the colour of water such that it is
darker than refracted terrain
+ also disabled sunlight scattering at night. This may actually be
desirable, but given there is no visible moon it seems unlikely to make
much sense, and blends a lot of green into the water colour appearing
luminescent at night
Fixed underwater issue

I had accidentally deleted some interpolation parameters.
fixed base flag in content file loader code
Merge remote-tracking branch 'filkry/bug640_luminescent_water'
Merge remote-tracking branch 'scrawl/master'
Fix for compiling Win32 debug.
Fix some MSVC warnings.

Several fixes are warnings about truncations on 64-bit, while others are
complaints about mixed signed / unsigned integer operations.
Fix MSVC size_t conversion warning.
Merge remote-tracking branch 'scrawl/master'
Merge branch 'master' of https://github.com/OpenMW/openmw

Conflicts:
	apps/openmw/mwrender/sky.hpp