osdep: add qemu_unlink()

Add a helper function to match qemu_open() which may return files
under the /dev/fdset prefix. Those shouldn't be removed, since it's
only a qemu namespace.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

include/qemu/osdep.h

@@ -462,6 +462,7 @@ int qemu_mprotect_none(void *addr, size_t size);
 
 int qemu_open(const char *name, int flags, ...);
 int qemu_close(int fd);
+int qemu_unlink(const char *name);
 #ifndef _WIN32
 int qemu_dup(int fd);
 #endif