[Ada] Add insertion character to Ineffective_Inline_Warnings messages

[Pierre-Marie de Rodat via Gcc-patches]

This enables tools that ingest GNAT's output to properly classify these
messages.

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

gcc/ada/

        * inline.adb (Check_Package_Body_For_Inlining): Add insertion
        character.
diff --git a/gcc/ada/inline.adb b/gcc/ada/inline.adb
--- a/gcc/ada/inline.adb
+++ b/gcc/ada/inline.adb
@@ -2804,8 +2804,8 @@ package body Inline is
                   elsif Ineffective_Inline_Warnings then
                      Error_Msg_Unit_1 := Bname;
                      Error_Msg_N
-                       ("unable to inline subprograms defined in $??", P);
-                     Error_Msg_N ("\body not found??", P);
+                       ("unable to inline subprograms defined in $?p?", P);
+                     Error_Msg_N ("\body not found?p?", P);
                      return;
                   end if;
                end if;