Support loading fonts again

This was... not fun, lots of `*const [*:0]u8` vs `[31:0]u8` and such
sillyness.  What worked in the end was a code example from [1] and a fix
from [2].

[1]: https://github.com/ziglang/zig/blob/c82c3585c8fdf02820747c118c78957e2eb5d072/lib/std/special/test_runner.zig#L17
[2]: https://github.com/ziglang/zig/issues/1481#issuecomment-806459027

c/sdl/hello_sdl.zig

    @cInclude("SDL2/SDL.h");
    @cInclude("SDL2/SDL_ttf.h");
});
const assert = @import("std").debug.assert;
const process = @import("std").process;
const std = @import("std");
pub fn main() !void {
    var general_purpose_allocator = std.heap.GeneralPurposeAllocator(.{}){};
    const gpa = &general_purpose_allocator.allocator;
    const args = try std.process.argsAlloc(gpa);
    defer std.process.argsFree(gpa, args);
    if (c.SDL_Init(c.SDL_INIT_VIDEO) != 0) {
        c.SDL_Log("Unable to initialize SDL: %s", c.SDL_GetError());
        return error.SDLInitializationFailed;
    }
    defer c.TTF_Quit();
    var font_file = "./FantasqueSansMono-Regular.ttf";
    var font_file = if (args.len > 1) args[1] else "./FantasqueSansMono-Regular.ttf";
    const font = c.TTF_OpenFont(font_file, 20) orelse {
        c.SDL_Log("Unable to load font: %s", c.TTF_GetError());
        return error.TTFInitializationFailed;
    };
    defer c.TTF_CloseFont(font);
    c.SDL_Log("Using font %s", font_file.ptr);
    const msg = "howdy there, enby! 🐘                                          ";
    c.SDL_Log(msg);