New release checklist

[refi64]

Fbuild hasn't had a release in years. It's time for that to change!!

• Make sure MinGW works again.
• Clean up the flags vs cflags vs lflags debacle.
• Add the ability to add flags to a C/C++ builders after it's been guessed. EDIT: Not doing this. You can just pass kw around manually.
• Improve installation support.
• Create binary variants (Nuitka? PyInstaller?) and probably a portable, single-file Python script (a.l.a. pfbuild). EDIT: Single-file Python script is done, and that's all I'm doing.
• More docs!
• Add recursive glob support (should be able to just backport the glob module).
• ...

[refi64]

Portable script done in 7de916a.

[refi64]

Recursive globbing done in d5b00b0.

[refi64]

Improved install done in 90d653a.