Emit a deprecation warning when dealing with incorrectly encoded strings

[byroot]

Ref: #138

Because it was initially implemented for Ruby 1.8 which didn't have proper string encoding, in a bunch of places the C version does silently accept strings with broken encodings.

We should emit a deprecation warning in 2.8.0, and remove that mis-feature in 3.0

• json/ext/json/ext/parser/parser.rl

  Line 693 in fb25e94

  // TODO: Deprecate in 2.8.0

• json/ext/json/ext/generator/generator.c

  Line 768 in fb25e94

  // TODO: Deprecate in 2.8.0