[Ada] Remove duplicated routines for getting homonym number

[Ada] Remove duplicated routines for getting homonym number

Routines Homonym_Number and Get_Homonym_Number were exactly the same,
except for minor style differences. Keep the one in Exp_Util; remove the
one in Exp_Dbug. No test attached, because semantics is unaffected.

2019-09-19  Piotr Trojanek  <trojanek@adacore.com>

gcc/ada/

	* exp_dbug.ads, exp_dbug.adb (Get_Homonym_Number): Remove.
	(Append_Homonym_Number): Use Homonym_Number instead of
	Get_Homonym_Number.
	* exp_util.ads, exp_util.adb (Homonym_Number): Mirror style of
	the removed Get_Homonym_Number routine, i.e. initialize local
	objects at declaration and refine the type of result.
	* sem_util.adb (Add_Homonym_Suffix): Use Homonym_Number instead
	of Get_Homonym_Number.

From-SVN: r275940