Handle NULL gracefully in json_tokener_free

Fix underline bug in README

Add fuzz tests for json_object/point/array apis

Extends the coverage of fuzz tests executed in OSS-Fuzz.

Similarly to glibc's free, make json_tokener_free(NULL)
a no-op, to simplify cleanup paths.

Signed-off-by: Ján Tomko <jtomko@redhat.com>

Correct year in changelog for 0.18 release

Issue #867: disallow control characters in strict mode.

Build pkg-config for msvc as well

Handle yet another out-of-memory condition.

duplocale() can return NULL, with errno set to ENOMEM.
In this case, bail out and set the current error code to
json_tokener_error_memory.

json_tokener.h: json_tokener_parse_verbose: fix typo

https://github.com/doxygen/doxygen/issues/10466

docs: micro typo in json_object_put doc

rename WIN32 to _WIN32

The latter is the proper macro defined by Windows headers.

Fixes compilation under at least clang-cl which mandates function
declarations.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

random_seed.c: add a Coverity Scan suppression

Coverity Scan warns about the use of open() after stat() being a
potential TOCTOU (Time of check time of use) issue. But here there is no
such issue.

Use execute_process instead of exec_program

Replace with `execute_process` available on v3.0+

Now saved to variable.

There are many others that show up if we were to add -Wsign-conversions,
but this is the only one using a literal constant.