Document s% and s# for json_pack, s% for json_unpack

doc/apiref.rst

@@ -1113,6 +1113,11 @@ arguments.
 
     .. versionadded:: 2.5
 
+``s%`` (string) [const char \*, size_t]
+    Like ``s#`` but the length argument is of type :type:`size_t`.
+
+    .. versionadded:: 2.6
+
 ``+`` [const char \*]
     Like ``s``, but concatenate to the previous string. Only valid
     after ``s``, ``s#``, ``+`` or ``+#``.
@@ -1125,6 +1130,11 @@ arguments.
 
     .. versionadded:: 2.5
 
+``+%`` (string) [const char \*, size_t]
+    Like ``+#`` but the length argument is of type :type:`size_t`.
+
+    .. versionadded:: 2.6
+
 ``n`` (null)
     Output a JSON null value. No argument is consumed.
 
@@ -1239,6 +1249,12 @@ type whose address should be passed.
     :func:`json_string_value()` internally, so it exists as long as
     there are still references to the corresponding JSON string.
 
+``s%`` (string) [const char \*, size_t *]
+    Convert a JSON string to a pointer to a NULL terminated UTF-8
+    string and its length.
+
+    .. versionadded:: 2.6
+
 ``n`` (null)
     Expect a JSON null value. Nothing is extracted.
 

doc/conformance.rst

@@ -19,15 +19,8 @@ Strings
 =======
 
 JSON strings are mapped to C-style null-terminated character arrays,
-and UTF-8 encoding is used internally. Strings may not contain
-embedded null characters, not even escaped ones.
-
-For example, trying to decode the following JSON text leads to a parse
-error::
-
-    ["this string contains the null character: \u0000"]
-
-All other Unicode codepoints U+0001 through U+10FFFF are allowed.
+and UTF-8 encoding is used internally. All Unicode codepoints U+0000
+through U+10FFFF are allowed.
 
 Unicode normalization or any other transformation is never performed
 on any strings (string values or object keys). When checking for