ada: Replace spinlocks with fully-fledged locks in finalization collections

ada: Replace spinlocks with fully-fledged locks in finalization collections

This replaces spinlocks with fully-fledged locks in finalization collections
because the former are deemed problematic with tasks that can be preempted.

Because of the requirement to avoid dragging the tasking runtime when it is
not necessary, the implementation goes through the usual soft links, with an
additional hurdle that space must be reserved for the lock in any case since
it is part of the ABI.  This entails the introduction of the System.OS_Locks
unit in the non-tasking runtime and the modification of the tasking runtime
to also use this unit.

This in turn requires a small adjustment: because of the presence of pre-
and post-conditions in Interfaces.C and of the limitations of the RTSfind
mechanism, the System.Finalization_Primitives unit must be preloaded, as
what is done for the Ada.Strings.Text_Buffers unit.

This effectively reverts the implementation to using the global task lock on
bare board platforms.

gcc/ada/

	* Makefile.rtl (GNATRTL_NONTASKING_OBJS): Add s-oslock$(objext).
	(LIBGNAT_TARGET_PAIRS): Use s-oslock__dummy.ads by default.
	Set specific s-oslock.ads source file for all the platforms.
	* exp_ch7.ads (Preload_Finalization_Collection): New procedure.
	* exp_ch7.adb (Allows_Finalization_Collection): Return False if
	System.Finalization_Primitives has not been preloaded.
	(Preload_Finalization_Collection): New procedure.
	* opt.ads (Interface_Seen): New boolean variable.
	* s-oscons-tmplt.c: Use "N" string for pragma Style_Checks.
	* scng.adb (Scan): Set Interface_Seen upon seeing "interface".
	* sem_ch10.adb: Add clause for Exp_Ch7.
	(Analyze_Compilation_Unit): Call Preload_Finalization_Collection
	after the context of the unit is analyzed.
	* libgnarl/a-rttiev.adb: Add with clause for System.OS_Locks and
	alphabetize others.
	(Event_Queue_Lock): Adjust qualified name of subtype.
	* libgnarl/s-osinte__aix.ads: Add with clause for System.OS_Locks
	and change pthread_mutex_t into a local subtype.
	* libgnarl/s-osinte__android.ads: Likewise.
	* libgnarl/s-osinte__darwin.ads: Likewise.
	* libgnarl/s-osinte__dragonfly.ads: Likewise.
	* libgnarl/s-osinte__freebsd.ads: Likewise.
	* libgnarl/s-osinte__gnu.ads: Likewise.
	* libgnarl/s-osinte__hpux-dce.ads: Likewise.
	* libgnarl/s-osinte__hpux.ads: Add Likewise.
	* libgnarl/s-osinte__kfreebsd-gnu.ads: Likewise.
	* libgnarl/s-osinte__linux.ads: Likewise.
	* libgnarl/s-osinte__lynxos178e.ads: Likewise.
	* libgnarl/s-osinte__qnx.ads: Likewise.
	* libgnarl/s-osinte__rtems.ads: Likewise.
	* libgnarl/s-osinte__mingw.ads: Add with clause for System.OS_Locks
	and change CRITICAL_SECTION into a local subtype.  Add declarations
	for imported procedures dealing with CRITICAL_SECTION.
	* libgnarl/s-osinte__solaris.ads: Add with clause for System.OS_Locks
	and change mutex_t into a local subtype.
	* libgnarl/s-osinte__vxworks.ads: Add missing blank line.
	* libgnarl/s-taprop.ads: Alphabetize clauses and package renamings.
	Use qualified name for RTS_Lock throughout.
	* libgnarl/s-taprop__dummy.adb: Add use clause for System.OS_Locks
	and alphabetize others.
	* libgnarl/s-taprop__hpux-dce.adb: Likewise.
	* libgnarl/s-taprop__linux.adb: Likewise.
	* libgnarl/s-taprop__posix.adb: Likewise.
	* libgnarl/s-taprop__qnx.adb: Likewise.
	* libgnarl/s-taprop__rtems.adb: Likewise.
	* libgnarl/s-taprop__solaris.adb: Likewise.
	* libgnarl/s-taprop__vxworks.adb: Likewise.
	* libgnarl/s-taprop__mingw.adb: Likewise.  Remove declarations for
	imported procedures dealing with CRITICAL_SECTION.
	* libgnarl/s-tarest.adb: Add with clause for System.OS_Locks and
	alphabetize others.
	(Global_Task_Lock): Adjust qualified name of subtype.
	* libgnarl/s-tasini.adb: Add clause for System.OS_Locks.
	(Initialize_RTS_Lock): New procedure.
	(Finalize_RTS_Lock): Likewise.
	(Acquire_RTS_Lock): Likewise.
	(Release_RTS_Lock): Likewise.
	(Init_RTS): Add compile-time assertions for RTS_Lock types.
	Set the soft links for the RTS lock manipulation routines.
	* libgnarl/s-taspri__dummy.ads: Add with clause for System.OS_Locks.
	(RTS_Lock): Delete and adjust throughout accordingly.
	* libgnarl/s-taspri__hpux-dce.ads: Likewise.
	* libgnarl/s-taspri__lynxos.ads: Likewise.
	* libgnarl/s-taspri__mingw.ads: Likewise.
	* libgnarl/s-taspri__posix-noaltstack.ads: Likewise.
	* libgnarl/s-taspri__posix.ads: Likewise.
	* libgnarl/s-taspri__solaris.ads: Likewise.
	* libgnarl/s-taspri__vxworks.ads: Likewise.
	* libgnat/s-finpri.ads: Add clause for System.OS_Locks.
	(Finalization_Collection): Change type of Lock.
	* libgnat/s-finpri.adb (Initialize): Call Initialize_RTS_Lock.
	(Lock_Collection): Call Acquire_RTS_Lock.
	(Unlock_Collection): Call Release_RTS_Lock.
	* libgnat/s-oslock__dummy.ads: New file.
	* libgnat/s-oslock__hpux-dce.ads: Likewise.
	* libgnat/s-oslock__mingw.ads: Likewise.
	* libgnat/s-oslock__posix.ads: Likewise.
	* libgnat/s-oslock__solaris.ads: Likewise.
	* libgnat/s-oslock__vxworks.ads: Likewise.
	* libgnat/s-soflin.ads (Null_Set_Address): New null procedure.
	(Initialize_RTS_Lock): New soft link.
	(Finalize_RTS_Lock): Likewise.
	(Acquire_RTS_Lock): Likewise.
	(Release_RTS_Lock): Likewise.
	* exp_ch4.adb (Expand_N_Allocator): In the subtype indication case,
	call Apply_Predicate_Check on the resulting access value if need be.