In NandPaths.cpp, the `std::initializer_list<char>` of illegal characters has been turned into a `char[]` (similar to the one in GameList.cpp).

The reverse iteration in ResourcePack.cpp seemed to provide no benefits, and doing without it it seemed to have no ill effects.

SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

Continues the migration to using fmt.

Notably, this allows safely converting a map within USBUtils over to
containing string view instances, rather than std::string instances, as
fmt safely handles the formatting of string views.

Xlib has really terrible headers that declare non-namespaced
macros and typedefs for common words.

Just wasted 10 minutes trying to figure out why a unit test failed
to build before I remembered it was Xrandr.h conflicting with our
enum class members again.

To fix the issue, this removes the Display* parameter from the
EnableScreensaver function (which was unused) so we don't have
to include Xrandr.h anymore.