Fix sources after enforcing RM 8.6(27.1) in the compiler

* lsp-gpr_handlers.adb (Get_Parsed_File): Add explicit type conversion.
* lsp-default_message_handlers.adb (Initialize): Add explicit type conversion.

For eng/toolchain/gnat#1292

Author: miranda-adacore

source/gpr/lsp-gpr_handlers.adb

@@ -134,11 +134,12 @@ package body LSP.GPR_Handlers is
          declare
             Parsed_File : constant Internal_File_Access :=
               new LSP.GPR_Files.File (Self.Tracer);
+            use LSP.GPR_Files;
 
          begin
             Parsed_File.Initialize
               (Path          => Path,
-               File_Provider => Self);
+               File_Provider => File_Provider_Access (Self));
 
             Self.Parsed_Files.Insert (Path, Parsed_File);
 

source/server/lsp-default_message_handlers.adb

@@ -96,7 +96,7 @@ package body LSP.Default_Message_Handlers is
         LSP.Server_Message_Visitors.Server_Message_Visitor'Class;
       Priority : LSP.Server_Jobs.Job_Priority := LSP.Server_Jobs.Fence) is
    begin
-      Self.Handler := Handler;
+      Self.Handler  := Server_Message_Visitor_Access (Handler);
       Self.Priority := Priority;
    end Initialize;