[Ada] Documentation of Img attribute out of date

[Ada] Documentation of Img attribute out of date

2019-07-10  Justin Squirek  <squirek@adacore.com>

gcc/ada/

	* doc/gnat_rm/implementation_defined_attributes.rst: Add mention
	of 'Image attribute with 'Img's entry to mention additional
	added 2012 usage of Obj'Image.
	* doc/gnat_rm/implementation_defined_pragmas.rst: Correct
	mispelling of Async_Writers.
	* gnat_rm.texi: Regenerate.
	* sem_prag.adb (Analyze_Pragma): Correct mispelling of
	Async_Writers.
	* sem_util.adb (State_Has_Enabled_Property): Correct mispelling
	of Async_Writers.

From-SVN: r273344