[Ada] Disable expansion of pragma Loop_Variant in CodePeer mode

[Pierre-Marie de Rodat via Gcc-patches]

Pragma Loop_Variant is expanded into code which is too complicated for
CodePeer to handle and results in messages with internal names. Disable
expansion.

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

gcc/ada/

        * exp_prag.adb (Expand_Pragma_Loop_Variant): Disable expansion
        in CodePeer mode.
diff --git a/gcc/ada/exp_prag.adb b/gcc/ada/exp_prag.adb
--- a/gcc/ada/exp_prag.adb
+++ b/gcc/ada/exp_prag.adb
@@ -2692,8 +2692,11 @@ package body Exp_Prag is
    begin
       --  If pragma is not enabled, rewrite as Null statement. If pragma is
       --  disabled, it has already been rewritten as a Null statement.
+      --
+      --  Likewise, do this in CodePeer mode, because the expanded code is too
+      --  complicated for CodePeer to analyse.
 
-      if Is_Ignored (N) then
+      if Is_Ignored (N) or else CodePeer_Mode then
          Rewrite (N, Make_Null_Statement (Loc));
          Analyze (N);
          return;