[Ada] Use source casing in messages for aliasing checks

[Pierre-Marie de Rodat <derodat@adacore.com>]

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When compiling code with -gnateA -gnateE switches, i.e. with aliasing
checks and extra information in exception messages, the runtime error
includes names the overlapping formal parameters. Those parameters are
now printed exactly as they appear in the source code, not in casing
that has been determined for the compilation unit.

For example, error emitted for GNATprove included name "Fa" for a formal
parameter that appears in the code as "FA", because GNATprove uses mixed
case coding convention (just like GNAT).

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* checks.adb (Overlap_Check): Replace Set_Casing with
	Adjust_Name_Case and adapt surrounding code as needed.

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diff --git a/gcc/ada/checks.adb b/gcc/ada/checks.adb
--- a/gcc/ada/checks.adb
+++ b/gcc/ada/checks.adb
@@ -24,7 +24,6 @@
 ------------------------------------------------------------------------------
 
 with Atree;          use Atree;
-with Casing;         use Casing;
 with Debug;          use Debug;
 with Einfo;          use Einfo;
 with Einfo.Entities; use Einfo.Entities;
@@ -2417,9 +2416,8 @@ package body Checks is
          Formal_2 : Entity_Id;
          Check    : in out Node_Id)
       is
-         Cond      : Node_Id;
-         ID_Casing : constant Casing_Type :=
-                       Identifier_Casing (Source_Index (Current_Sem_Unit));
+         Cond        : Node_Id;
+         Formal_Name : Bounded_String;
 
       begin
          --  Generate:
@@ -2451,15 +2449,17 @@ package body Checks is
 
             Store_String_Chars ("aliased parameters, actuals for """);
 
-            Get_Name_String (Chars (Formal_1));
-            Set_Casing (ID_Casing);
-            Store_String_Chars (Name_Buffer (1 .. Name_Len));
+            Append (Formal_Name, Chars (Formal_1));
+            Adjust_Name_Case (Formal_Name, Sloc (Formal_1));
+            Store_String_Chars (To_String (Formal_Name));
 
             Store_String_Chars (""" and """);
 
-            Get_Name_String (Chars (Formal_2));
-            Set_Casing (ID_Casing);
-            Store_String_Chars (Name_Buffer (1 .. Name_Len));
+            Formal_Name.Length := 0;
+
+            Append (Formal_Name, Chars (Formal_2));
+            Adjust_Name_Case (Formal_Name, Sloc (Formal_2));
+            Store_String_Chars (To_String (Formal_Name));
 
             Store_String_Chars (""" overlap");