Given this is actually a part of the Host interface, this should be
placed with it.

While we're at it, turn it into an enum class so that we don't dump its
contained values into the surrounding scope. We can also make
Host_Message take the enum type itself directly instead of taking a
general int value.

After this, it'll be trivial to divide out the rest of Common.h and
remove the header from the repository entirely

After 3a83ebc, the Show System Clock feature started using the
unfortunate combination of MM/DD/YY dates (rare outside of the US)
and 24-hour time (rare in the US) regardless of the user's locale
settings. This commit makes it use the configured locale again.

I've noticed one minor difference in behavior between now and
before 3a83ebc: The new way of setting the C/C++ locale seems to
treat "en" as "en-US", but the wx way of setting the C locale
treated it as "en-GB" (at least on Windows).

BootParameters can now contain the path of a savestate to load at boot.
Movie has been made to use this instead of poking at Core.cpp's state.

WX: Fix argument parsing

Fixes issue 10685

Manually convert each argument to a UTF-8 std::string, because the
implicit conversion for wxCmdLineArgsArray to char** calls ToAscii
(which is obviously undesired).

Fixes https://bugs.dolphin-emu.org/issues/10274

Ideally Common.h wouldn't be a header in the Common library, and instead be renamed to something else, like PlatformCompatibility.h or something, but even then, there's still some things in the header that don't really fall under that label

This moves the version strings out to their own version header that doesn't dump a bunch of other unrelated things into scope, like what Common.h was doing.

This also places them into the Common namespace, as opposed to letting them sit in the global namespace.