Replaced directory-wide add_compile_definitions/add_definitions with
target_compile_definitions PRIVATE on the shared lib target, so
JSON_DLL_BUILD is not incorrectly applied to static and object libs.

Fixes #1634

IStringStream inherits the global locale, so parsing doubles with
operator>> fails when the locale uses ',' as the decimal separator
(e.g. de_DE). Imbue the stream with std::locale::classic() in both
Reader::decodeDouble and OurReader::decodeDouble.

The writer already handles this correctly via fixNumericLocale().

Fixes #1565

RFC 8259 requires that control characters (U+0000-U+001F) be escaped
when they appear inside strings. jsoncpp previously accepted them
silently. Add a check in Reader::decodeString and
OurReader::decodeString to return an error when an unescaped control
character is encountered.

Fixes #1546

* Fix MSAN issue in #1626

This patch fixes an MSAN issue by changing CZString
initialization.

* add test

* expand tests

* fix build

* Export CZString with JSON_API to fix Windows DLL linker errors

The library was forced to build with CMAKE_CXX_STANDARD 11, so
JSONCPP_HAS_STRING_VIEW was never defined at compile time. Consumers
building with C++17 would see the string_view APIs in the header but
fail to link them.

Fix:
- Remove the global CMAKE_CXX_STANDARD 11 override; the existing
  target_compile_features(cxx_std_11) already enforces the minimum.
- Detect string_view support at configure time with
  check_cxx_source_compiles and export JSONCPP_HAS_STRING_VIEW as a
  PUBLIC compile definition on all library targets, so consumers
  always see the same value the library was built with.
- Guard the __cplusplus fallback in value.h so it does not override
  the CMake-set define.

Fixes #1595

* Revert "Fix number parsing failing under non-C locales (#1662)"

This reverts commit 8661f9e.

* readd json reader changes

The istream overload stored the document in a local String then
passed raw pointers into it to parse(const char*, const char*),
which kept those pointers in begin_/end_. After parse() returned
the local String was destroyed, leaving begin_/end_ dangling.
Any subsequent call to getFormattedErrorMessages() would then
read freed memory.

Fix by reading the stream into the member document_ instead, matching
the behavior of parse(const std::string&).

Also document the lifetime requirement on parse(const char*, const
char*): the caller's buffer must outlive the Reader if error-reporting
methods are used after parsing.

Fixes #1623