Fix syntax errors in bash versions < 5.2

[lj3954]

Fixes #5

[dabrown645]

I noticed you removed TMPDIR from quickget, it is used by some plugins to pass information between functions via files to avoid remaking expensive calls out to the web.

[dabrown645]

Based on you comments about spelling/typing errors I have run aspell on all the files and made corrections and pushed up to github.

Oops. I backed the change out as I didn't so enough testing and broke it I will be redoing to correct this.

[lj3954]

Global variables do the job, temporary files aren't needed to store this type of information. Remember, you're using the source command, which runs every line of the code in whatever file you call it on, essentially adding all functions in the plugin file on the top of all the functions in quickget.

I very much am in favor of the idea of a plugin type system for quickget operating systems. I think it will clean up the code significantly and allow for many more options and features to be implemented, especially for individual operating systems which need unique methods of downloading, unarchiving, and the like. However, I don't really like the way you've set this all up. The distro_info array with fixed values, mandatory editions function, and other functions which I find way too hardcoded for my liking. Creating a windows plugin gave me so many issues I figured the simplest way to accomplish the task while maintaining your structure would have been to take complete control, overriding nearly every single function in quickget, because of the issues they were causing. Thus, I'm working on creating my own version of quickget with plugins instead, in a way that's more friendly to OS additions. I wish you luck on what you're attempting here, but I believe it's gone too far in the wrong direction for me to contribute.