tests|lib: remove assert.h includes

Only the igt core and non-test tools should have asserts to catch
internal errors, tests and helper libraries should all user igt_asert
instead.

Fix things up where assert instead of igt_assert was used.

One tiny step towards header sanity.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

lib/igt_core.c

@@ -32,6 +32,7 @@
 #include <libgen.h>
 #endif
 #include <stdio.h>
+#include <assert.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/ioctl.h>