Prefix ocamldebug modules to minimize clashes

Prefix ocamldebug modules with 'ocamldebug_' to minimize eventual
clashes with user modules when running load_printer.

Some modules already had the 'debugger_' prefix. For those, we replaced
'debugger_' with 'ocamldebug_'.

.gitignore

@@ -73,9 +73,9 @@ _build
 /bytecomp/opcodes.ml
 /bytecomp/opcodes.mli
 
-/debugger/debugger_lexer.ml
-/debugger/debugger_parser.ml
-/debugger/debugger_parser.mli
+/debugger/ocamldebug_lexer.ml
+/debugger/ocamldebug_parser.ml
+/debugger/ocamldebug_parser.mli
 /debugger/ocamldebug
 
 /emacs/ocamltags