* common/config/aarch64/aarch64-common.c (aarch64_handle_option):
	Handle OPT_moutline_atomics.
	* config/aarch64/aarch64.c: Add outline-atomics to
	aarch64_attributes.

	* doc/extend.texi: Document the newly added target attribute.

	* gcc.target/aarch64/target_attr_20.c: New test.
	* gcc.target/aarch64/target_attr_21.c: New test.

(cherry picked from commit 9e02b45ffc60e0078bde3c56a14f00c54b7f8039)