2019-10-10  Bob Duff  <duff@adacore.com>

gcc/ada/

	* libgnat/a-cbdlli.adb, libgnat/a-cbhama.adb,
	libgnat/a-cbhase.adb, libgnat/a-cbmutr.adb,
	libgnat/a-cborma.adb, libgnat/a-cborse.adb,
	libgnat/a-cdlili.adb, libgnat/a-cidlli.adb,
	libgnat/a-cihama.adb, libgnat/a-cihase.adb,
	libgnat/a-cimutr.adb, libgnat/a-ciorma.adb,
	libgnat/a-ciorse.adb, libgnat/a-cobove.adb,
	libgnat/a-cohama.adb, libgnat/a-cohase.adb,
	libgnat/a-coinve.adb, libgnat/a-comutr.adb,
	libgnat/a-conhel.adb, libgnat/a-convec.adb,
	libgnat/a-coorma.adb, libgnat/a-coorse.adb (Reference,
	Constant_Reference): Use Busy instead of Lock, so we forbid
	tampering with cursors, rather than tampering with elements.

From-SVN: r276813