Add JSON.pm to third_party

third_party/JSON/JSON-2.59/t/15_prefix.t

Index: third_party/JSON/JSON-2.59/t/15_prefix.t
diff --git a/third_party/JSON/JSON-2.59/t/15_prefix.t b/third_party/JSON/JSON-2.59/t/15_prefix.t
new file mode 100644
index 0000000000000000000000000000000000000000..3071be277f8f6b4a0860c742a9be5da3e772cc53
--- /dev/null
+++ b/third_party/JSON/JSON-2.59/t/15_prefix.t
@@ -0,0 +1,16 @@
+# copied over from JSON::XS and modified to use JSON
+
+BEGIN { $| = 1; print "1..4\n"; }
+BEGIN { $ENV{PERL_JSON_BACKEND} = "JSON::backportPP"; }
+
+use JSON;
+
+my $xs = JSON->new->allow_nonref;
+
+eval { $xs->decode ("[] ") };
+print $@ ? "not " : "", "ok 1\n";
+eval { $xs->decode ("[] x") };
+print $@ ? "" : "not ", "ok 2\n";
+print 2 == ($xs->decode_prefix ("[][]"))[1] ? "" : "not ", "ok 3\n";
+print 3 == ($xs->decode_prefix ("[1] t"))[1] ? "" : "not ", "ok 4\n";
+