man-pages-3.28 is released

I've uploaded man-pages-3.28 into the release directory (or view the online pages). The most notable changes in man-pages-3.28 are as follows:

• A new getaddrinfo_a(3) page documents the getaddrinfo_a(3), gai_suspend(3), gai_cancel(3), and gai_error(3) library functions. Thanks to Petr Baudis.
• A new aio(7) page provides an overview of the POSIX asynchronous I/O API.
• Various improvements were made to the section 3 pages describing the POSIX asynchronous I/O API: aio_cancel(3), aio_error(3), aio_fsync(3), aio_read(3), aio_return(3), aio_suspend(3) and aio_write(3).
  
• The exec(3) page adds documentation for the execvpe(3) library function.
• Continuing the work of man-pages-3.27, information about feature test macro requirements was improved in various pages.