support unicode escapes in the pure lua json decoder

json.decode(str, {pure = true}) dropped the backslash-u of \uXXXX
escapes and kept the following four hex digits verbatim, e.g.
"a\u0041b" decoded to "au0041b" instead of "Ab", while the C
decoder returns "Ab".

Decode \uXXXX escapes to UTF-8 in the pure decoder, combine surrogate
pairs, e.g. \uD83D\uDE00, and raise an error for invalid or lone
surrogate escapes, matching the behavior of the C decoder.

0 files changed, 0 insertions, 0 deletions