test_parsing files are stored in latin1, not utf8 encoding

[cookiengineer]

A quick glance over some files inside the test_parsing folder show that most of the files that don't run through the JS-native JSON.parse() method are actually encoded in latin1 and not in utf8, therefore cannot be handled correctly for probably any other parser, too.

Example file: https://github.com/nst/JSONTestSuite/blob/master/test_parsing/i_string_truncated-utf-8.json