Fix gcc warnings.

[GandaG]

Fixes the not a prototype warning that thread_hold() gives, fixes the unused argument that comes up after fixing the previous one and fixes the unused argument that thpool_resumes() gives.

[Pithikos]

Do you think you could provide a few details on how you compile the library and/or how you run it? Compiling the below I don't get any warnings from the compiler and I can run the example.

gcc example.c thpool.c -D THPOOL_DEBUG -pthread -o example

I was getting warnings in case I used the -std=c99 but I fixed that with the latest commit @a3916021c837e4892667e02e1681437ddc362725.

[GandaG]

That example has no warnings enabled, I usually use: -Wall -Wextra -Wstrict-prototypes.

-Wall is absolutely essential and it gives you warnings for the most common and easy to fix mistakes. It doesn't actually enable all warnings.

-Wextra gives warnings about some things that may result in undefined behaviour, like comparing unsigned with signed types.

-Wstrict-prototypes is mostly personal preference but I like to make sure when I look at my forward declarations that I understand what the function is and it doesn't really hurt either way :)

[Pithikos]

Thanks, it makes sense now.

I think this is ready to go. Just a minor thing. Regarding the (void)thpool_p; in thpool_resume I think it's worth to add a comment making it clear that the idea is to resume threads on a threadpool basis but that has not been implemented yet #13. Else it might be a bit confusing and a bit of danger that someone totally removes the (void)thpool_p; line in the future.

[Pithikos]

Thanks for the help!