Fixes bug [#4678](https://gitlab.com/OpenMW/openmw/issues/4678)
The `loadSCVR` method assumes that the list of variable
names won't be empty, which it might.
Instead of crashing, we show a warning and ignore the record.
This change aims to allow TES4/TE5 content to OpenMW. i.e. a standalone TES4 would be implemented quite differently. That said, the key changes are:
* Use pointers rather than references for ESM readers so that they can be switched to another variant on the fly.
* Content file dependencies to be checked within each group (only 3 groups for now, TES3/TES4/TES5)
* Implement hash based lookup for TES3 BSA files.
* Added TES4/TES5 BSA support.
* Implemented a hack (non-portable code) in an attempt to reduce startup time under Windows because Boost::filesystem seems to take forever on GetFileAttributeW. This implementation uses FindFirstFile/FindNextFile/FindClose instead.
The resizing of LTEX store to the correct number of plugins was done in the load() method, but the load method won't be called if a plugin contains LAND records but doesn't contain LTEX records. For such plugins the Store<ESM::LandTexture>::search() function would then fail an assertion.
(cherry picked from commit 4687c4baad)
# Conflicts:
# apps/openmw/mwworld/store.cpp
# apps/openmw/mwworld/store.hpp
Note, I suspect Rng::rollClosedProbability() is not needed. The only difference between it and rollProbability() is that one time in 37k (on Windows), it will give an output of 1.0.
On some versions of Linux, the value of 1.0 will occur about 1 time in 4 billion.
(cherry picked from commit 3f28634d1f)
# Conflicts:
# apps/openmw/mwclass/creature.cpp
# apps/openmw/mwclass/npc.cpp
# apps/openmw/mwgui/pickpocketitemmodel.cpp
# apps/openmw/mwgui/waitdialog.cpp
# apps/openmw/mwmechanics/combat.cpp
# apps/openmw/mwmechanics/mechanicsmanagerimp.cpp
# components/CMakeLists.txt
# libs/openengine/misc/rng.cpp
