For the specific mods that work around engine-level
bugs but should not be applied redundantly, add
feature flags, and don't apply the fix if the feature
flag is already present.

This should allow these fixes to be included in
base games without them interfering if the modular
versions from szutilpack are also enabled.

Ideally, games should optionally depend on the
szutilpack implementations to ensure one of them
always takes precedence, so that server owners will
know ahead of time which configuration settings
they should apply, and the more configurable
version (which should ideally be szutilpack) will
apply.