docs: update to Internet Standard reference

This gets us up to a version that supports features we're already using
(i.e. add_compile_options), but stops short of a cmake that requires
c++11, which some OSes still don't support.
Closes issue #774

Problem: cmake 3.25.1 warns about CMP0042 not being set

Problem: confusing error message in snprintf_compat.h

Problem: modern CMake warns about version 2.8

Solution: set it explictly to OLD behavior

Solution: fix it to reflect what's happening properly

The warning is as follows:

```
Compatibility with CMake < 2.8.12 will be removed from a future version of CMake.
```

Solution: set it at 2.8.12

Added Test for get int functions

Small update to README file

it could be necessary to execute make install

get_time_seed(): silence warning emitted by Coverity Scan static analyzer

It warns about the return of time() being truncated to 32 bit, which is
not an issue here.
(this warning was emitted because of the https://github.com/OSGeo/gdal
project embedding a copy of libjson-c and running Coverity Scan
analysis)

Fix build with clang-15+

This helps compiling with MS compiler, error seems to be
due to defining a variable within the body of the function
its allowed in c99 but not in c89. This should fix build with
MSVC 16.0.40219.1 compiler from Visual Studio 14 2015

Signed-off-by: Khem Raj <raj.khem@gmail.com>

Signed-off-by: Khem Raj <raj.khem@gmail.com>

Fixes
json_util.c:63:35: error: a function declaration without a prototype is deprecated in all versions of C [-We
rror,-Wstrict-prototypes]
const char *json_util_get_last_err()
                                  ^
                                   void

Signed-off-by: Khem Raj <raj.khem@gmail.com>

Fix typos found by codespell

Do not fix typos from past commits found in release notes.

json_object_from_fd_ex: fail if file is too large

Fix memory leak with emtpy strings in json_object_set_string

When a json string object is updated with a bigger string, a new
malloc'ed buffer is used to store the new string and it's size is made
negative to indicate that an external buffer is in use.

When that same json string object get's updated again with an empty
stirng (size = 0), the new external malloc'ed buffer is still used.
But the fact that the new size value is not negative removes the
indicator that the externally malloc'ed buffer is used.

This becomes a problem when the object get's updated again with any
other string, because a new buffer will be malloced and linked to the
object while to old one won't be free'd.

This causes a memory leak when updating a json string with
json_object_set_stirng() which has previously been updated
with an empty string.

Example:
--
obj = json_object_new_string("data");
json_object_set_string(obj, "more data");
json_object_set_string(obj, "");
json_object_set_string(obj, "other data"); /* leaks */
--

This commit fixes the issue by free'ing the external buffer when an
empty string is set and use the internal one again.

Signed-off-by: Daniel Danzberger <daniel@dd-wrt.com>

Fix typo

Issue #768

Use target_link_libraries, plus fill in Libs.private in json-c.pc so pkg-config --static --libs works appropriately.
Also, only link against libbsd when arc4random is actually found there.

cmake rules matters, and fix compile warnings now that we're building
those sources with all the regular flags.