[Ada] Remove processing of SPARK_05 restriction

[Ada] Remove processing of SPARK_05 restriction

2020-06-08  Arnaud Charlet  <charlet@adacore.com>

gcc/ada/

	* exp_aggr.adb, exp_ch6.adb, par-ch11.adb, par-ch6.adb,
	par-ch7.adb, par-prag.adb, restrict.adb, restrict.ads,
	scans.ads, scng.adb, sem_aggr.adb, sem_attr.adb, sem_ch11.adb,
	sem_ch12.adb, sem_ch3.adb, sem_ch3.ads, sem_ch4.adb,
	sem_ch5.adb, sem_ch6.adb, sem_ch7.adb, sem_ch8.adb, sem_ch9.adb,
	sem_res.adb, sem_util.adb, sem_util.ads, snames.ads-tmpl,
	gnatbind.adb, libgnat/s-rident.ads,
	doc/gnat_rm/standard_and_implementation_defined_restrictions.rst:
	Remove processing of SPARK_05 restriction.
	* gnat_rm.texi: Regenerate.
	* opt.ads: Remove processing of old checksum which is now
	handled by gprbuild directly.