[Ada] Fix PR ada/87396

[Eric Botcazou]

Enumeration types are unsigned in Ada so use 'unsigned char' instead of 'char' 
for mapping Attribute_Id.

Tested x86-64/Linux, applied on the mainline.


2018-09-24  Eric Botcazou  <ebotca...@adacore.com>

        PR ada/87396
        * fe.h (Get_Attribute_Definition_Clause): Use 'unsigned char' instead
        of 'char' as the type of the second parameter.

-- 
Eric Botcazou
Index: fe.h
===================================================================
--- fe.h	(revision 264466)
+++ fe.h	(working copy)
@@ -85,7 +85,7 @@ extern void Set_RM_Size			(Entity_Id, Ui
 extern Boolean Is_Entity_Name		(Node_Id);
 
 #define Get_Attribute_Definition_Clause einfo__get_attribute_definition_clause
-extern Node_Id Get_Attribute_Definition_Clause (Entity_Id, char);
+extern Node_Id Get_Attribute_Definition_Clause (Entity_Id, unsigned char);
 
 /* errout: */