On first client start (when `cl_show_welcome` is `1`), determine the user locale with `os_locale_str` and initially select the most fitting language for this locale.
For this the language index must also be loaded immediately on client launch, before the initial language is loaded.
Add RFC 3066 language tags to language index in order to identify the language to select when first starting the game based on the user's locale.
Multiple language tags can be specified per entry separated with a semicolon, as some languages have different tags that do not share a unique prefix (e.g., Simplified and Traditional Chinese).
Purely automatic change. In case of conflict with this change, apply the
other change and rerun the formatting to restore it:
$ python scripts/fix_style.py
Also annotate `dbg_msg`, `str_format` and `str_timestamp_ex` so that the
compiler can determine whether the format strings are correct.
Fix the compiler warnings generated by these extra warnings -- some of
them were security issues.
