Clang-format sees the text behind `#pragma region` as code and formats it. Instead of stating the copyright and date there, it's now in the comment block right below it. The text "Copyright" is left in the `#pragma region` line, as clang-format sees it as a single identifier.
I took the opportunity to normalize the dates, and add the copyright notice to the source files where it was missing them (except for third-party and the generated resources.h file).
BannerIndex is defined in common.h (like some other types such as money32 and rct_string_id), so that banner.h wouldn't have to be includede everywhere. Later on, it may be nicer to have a custom types file instead of putting them all in common.h.
At some places, BANNER_NULL and BANNER_INDEX_NULL were mixed, and at one point even MAX_BANNERS, causing the 250th banner to not be initialized properly. This commit makes the uses of those defines correct, and changes all relevant functions to return uint8 instead of sint32.
The colour field in the banner object is also used to store the ride index when a banner is linked to a ride. This commit turns this field into a union with both named fields, to make the code clearer.
It also changes the return types of related functions to uint8 instead of sint32, and makes use of the RIDE_ID_NULL define where applicable.
This aims to make future refactoring easier. The arguments are removed where possible, but kept and marked with C++17's [[maybe_unused]] where they could not be removed (e.g. when they are used as a callback, rather than called directly).
I've skipped the rides/<category>/* and peep/* source files, because the rides source files are mostly generated and have a ton of unused variables, and the peep source files are being refactored.
I've also skipped most of window/* source files, because most of the functions are used as callbacks and will be bulk-renamed at some point.
Prior to the previous commit, signs could be duplicated by pasting them using the tile inspector, which results in some funky behaviour. A duplicated sign refers to the same banner index (which in turn refers to the same user string ID), making the player unable to modify it. Deleting it would previously even crash the game.
This commit looks for such signs when loading a scenario, and attempts to fix them, by creating a new banner entry (and user string if one is used).
