Remove redundant win32/unistd.h includes (#14533)

At this point win32/unistd.h only declares usleep which isn't used at
these places.

Clean-up unused headers (#14365)

* ext/mbstring.c: clean-up headers and include intrinsics

libmagic: Follow up fixes for 5.43

Fixes possible build and runtime issues on Windows.`

Signed-off-by: Anatol Belski <ab@php.net>

fileinfo: Introduce php_libmagic.* to simplify patch

Signed-off-by: Anatol Belski <ab@php.net>