Fixes for the XDG Base Dirs implementation (#330)

[Cavernosa]

Fixes errors/typos from #330 in order to better comply with the XDG Base Directory Specification:

• Renamed XDG_CONFIG_DIR to XDG_CONFIG_HOME
• added $HOME/.config/ as fallback in case XDG_CONFIG_HOME is null, and PWD as last resort.
• Filename for the PWD fallback now has a dot (.lyxauth instead of lyxauth) just like the other dotfiles in $HOME

I made some tests and it works fine. I'm a complete noob in C so I'd appreciate if someone reviews the code.

Note we should probably not use XDG_CONFIG_HOME at all since lyxauth is far from a config file. Using /run/user/$UID/ or /tmp/ would probably be better, and then maybe use pwd as the very last resort just in case, i don't really know.

[AnErrupTion]

Hmm, why storing .lyxauth in the root of .config? I believe having a separate directory for storing ly stuff is better than leaving it in the root of .config.

[Cavernosa]

I didn't think it was necessary since it's only 1 file. But yeah having it inside a directory doesn't hurt.
As i said we could remove XDG_CONFIG_HOME and ~/.config altogether but i'm not sure what would replace it... /tmp/ly/ is my biggest bet.

Edit: I quickly put together the /tmp/ly fallback and the changes you requested, pls tell which one you think is better:

	const char* xauth_file = "lyxauth";
	char* xauth_dir = getenv("XDG_RUNTIME_DIR");
	if ((xauth_dir == NULL) || (*xauth_dir == '\0'))
	{
		struct stat sb;
		stat("/tmp", &sb);
		if (S_ISDIR(sb.st_mode))
		{
			char template[] = "/tmp/ly-XXXXXX";
			xauth_dir = mkdtemp(template);
		}
		
		else
		{
			xauth_dir = pwd;
			xauth_file = ".lyxauth";			
		}
	}

The changes you requested (draft. i didn't try to check if ~/.config/ly folder exists as it's easier to just fallback to the pwd, and it doesn't check if a regular file named ly exists but that shouldn't be a big problem):

	const char* xauth_file = "lyxauth";
	char* xauth_dir = getenv("XDG_RUNTIME_DIR");
	if ((xauth_dir == NULL) || (*xauth_dir == '\0'))
	{
		xauth_dir = getenv("XDG_CONFIG_HOME");
		struct stat sb;
		if ((xauth_dir == NULL) || (*xauth_dir == '\0'))
		{
			xauth_dir = strdup(pwd);
			strcat(xauth_dir, "/.config/ly");
			stat(xauth_dir, &sb);
			if (!S_ISDIR(sb.st_mode))
			{
				xauth_dir = pwd;
				xauth_file = ".lyxauth";
			}
		}
		else
		{
			strcat(xauth_dir, "/ly");
			stat(xauth_dir, &sb);
			if (!S_ISDIR(sb.st_mode))
			{
				mkdir(xauth_dir, 0777);
			}
		}
	}

[AnErrupTion]

I prefer the second one (with .config/ly), I don't really like having the file in /tmp.

[Cavernosa]

Fixed.

[randomllama]

Why the 777 chmod?

[Cavernosa]

I think i forgot to change it lol. Weirdly, in my system the ly folder always appeared as 0755 instead of 0777.