headers: make more headers self-contained

alsa-project/alsa-lib pull request #435 was opened from timblechmann:

Some IDEs parse headers in isolation to populate their code model. This exposes some missing headers, mainly for alsa internal struct definitions, ssize_t (requiring sys/types.h), size_t (requiring string.h), va_args (requiring stdargs.h) or FILE (requiring stdio.h)

This patch makes the main headers parsable by qtcreator

Request URL : https://github.com/alsa-project/alsa-lib/pull/435 Patch URL : https://github.com/alsa-project/alsa-lib/pull/435.patch Repository URL: https://github.com/alsa-project/alsa-lib