liburcu: Update to version 0.15.1

liburcu: Update to version 0.15.1

- Update from version 0.15.0 to 0.15.1
- Update of rootfile not required
- Changelog
    0.15.1
	* uatomic/generic: Add missing #include <stdlib.h>
	* docs: Clarify that make is required to build the project
	* fix: add missing SPDX headers to urcu/uatomic/api.h
	* compiler.h: Remove caa_unqual_scalar_typeof

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>