gcc 4.7 programming question related to MythTV

I was trying to build the latest 0.24/fixes branch of MythTV and ran into an issue where many C files were using functions (usleep, write, close, gethostname, etc.) that were not available/(in scope?). It turns out that unistd.h provided these functions so I included it in all the offending files which allowed building to complete. Is there any reason this would be unsafe (or non-portable)? I've submitted a patch upstream but I'd like to get current builds out if there's no reason not to. Thanks, Richard