[Ada] Do full name qualification of local exception names for LLVM

[Pierre-Marie de Rodat]

Exceptions declared within subprograms are associated with objects
allocated statically (at the global level), and it's helpful for the
LLVM compiler (and likely others, such as CCG) if the exception name is
fully qualified, to avoid link name clashes (gcc-based GNAT has always
"uniquified" these names). GNAT was using the simple name for local
exceptions (as for other local objects), but it now uses fully qualified
names for all exceptions.

When compiled with the command:

gcc -c -gnatG local_exception.adb | grep "local_exception__local_exc"

the following output is generated for the test further below:

   local_exception__local_exc : static exception := (
        local_exception__local_exc'unrestricted_access));

procedure Local_Exception is

  Local_Exc : exception;

begin
   null;
end Local_Exception;

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

2019-08-13  Gary Dismukes  <dismu...@adacore.com>

gcc/ada/

        * exp_dbug.adb (Fully_Qualify_Name): Add full name qualification
        for the E_Exception case.
--- gcc/ada/exp_dbug.adb
+++ gcc/ada/exp_dbug.adb
@@ -1539,6 +1539,7 @@ package body Exp_Dbug is
       elsif Is_Subprogram (Ent)
         or else Ekind (Ent) = E_Subprogram_Body
         or else Is_Type (Ent)
+        or else Ekind (Ent) = E_Exception
       then
          Fully_Qualify_Name (Ent);
          Name_Len := Full_Qualify_Len;