[Ada] Enable the support of 128-bit integer types by default

[Ada] Enable the support of 128-bit integer types by default

gcc/ada/

	* Makefile.rtl (GNATRTL_128BIT_PAIRS): Add i-cexten.ads.
	* debug.adb (d.H): Document new usage.
	* doc/gnat_rm/representation_clauses_and_pragmas.rst (Size Clauses):
	Document new limit on 64-bit platforms.
	(Component_Size Clauses): Likewise.
	(Pragma Pack for Arrays): Likewise.
	(Pragma Pack for Records): Likewise.
	(Record Representation Clauses): Likewise.
	* gnat_rm.texi: Regenerate.
	* gnat1drv.adb (Adjust_Global_Switches): Rewrite code enabling or
	disabling the support for 128-bit integer types.
	* switch-c.adb (Scan_Front_End_Switches): Do not deal with e128.
	* usage.adb (Write_Switch_Char): Do not print -gnate128 switch.
	* libgnat/i-cexten__128.ads: New file.

gcc/testsuite/

	* ada/acats/run_all.sh: Define and substitute target_{max,min}_int.
	* ada/acats/support/macro.dfs: Parameterize {MAX,MIN}_INT.
	* gnat.dg/assert1.adb: Adjust conditionally to 128-bit integer types.
	* gnat.dg/size_clause1.adb: Do not expect a warning for LP64 targets.
	* gnat.dg/warn11.adb: Likewise.
	* gnat.dg/specs/rep_clause5.ads (Array_2_Type): Add alignment clause.