[perl #123514] Make prototype() imply $_

Previously it would read and replace the previous item on the stack:

$ ./perl -le 'print "CORE::undef", prototype'
;\[$@%&*]

1 files changed, 6 insertions, 0 deletions

diff --git a/proto.h b/proto.h
index c27e50b90b..cf8e93df61 100644
--- a/proto.h
+++ b/proto.h
@@ -570,6 +570,12 @@ PERL_CALLCONV OP *	Perl_ck_open(pTHX_ OP *o)
 #define PERL_ARGS_ASSERT_CK_OPEN	\
 	assert(o)
 
+PERL_CALLCONV OP *	Perl_ck_prototype(pTHX_ OP *o)
+			__attribute__warn_unused_result__
+			__attribute__nonnull__(pTHX_1);
+#define PERL_ARGS_ASSERT_CK_PROTOTYPE	\
+	assert(o)
+
 PERL_CALLCONV OP *	Perl_ck_readline(pTHX_ OP *o)
 			__attribute__warn_unused_result__
 			__attribute__nonnull__(pTHX_1);