ada: Fix abort deferral for finally parts

This patch fixes two problems with how abort was deferred in finally
parts. First, calls to runtime subprograms are now omitted when
aborting is disallowed by active restrictions. Second, Abort_Undefer is
now correctly called when the finally part propagates an exception.

gcc/ada/ChangeLog:

	* exp_ch11.adb (Expand_N_Handled_Sequence_Of_Statements): Fix abort
	deferral.