Ignore files generated by make check

[J-Lentz]

Description
Add a .gitignore file for each unit test, so that Git ignores all files generated by make check.

How Has This Been Tested?

make
make check -k
git status

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes

[rem1776]

it might be cleaner to put these all in the same root level .gitignore with file paths instead, I'm not sure its worth the effort though since that's basically personal preference.

I'll see what others think since these are hidden files anyway.