Add missing optparse_long_only() and useful macros for Windows, also separate definition and implementation.

[eeeeeeeelias]

No description provided.

[ShamrockLee]

It doesn't make sense to exclude function declarations and macro definitions when implementation is asked for.

AFAIK, forward declaration is a good practice when writing C. It not only guarentees the consistency between the header and the implementation, but also enables calling another function defined below the current one.

[ShamrockLee]

Are TCHAR and TEXT() macros still relevent? Could TCHAR be converted to int implicitly?
I'm not familiar with Windows. Please feal free to correct me.

https://docs.microsoft.com/en-us/windows/win32/learnwin32/working-with-strings

[brdjns]

It doesn't look like short options work properly when using optparse_long_only, and option order is screwy, too. Alongside the options from the repo examples, I've added -A as a short option corresponding to -amount:

./app -A --delay=4 --brief -a
./app: invalid option -- 'A'

Here, ambiguity doesn't work as intended:

./app-amend --delay=4 --brief -a
./app: option is ambiguous -- 'delay'