Patch by Blanca Elio Rosario.

Don't crash on deeply nested values by limiting parser recursion depth

The fix limits recursion depths when parsing arrays and objects.
The limit is configurable via the `JSON_PARSER_MAX_DEPTH` setting
within `jansson_config.h` and is set by default to 2048.

Update the RFC conformance document to note the limit; the RFC
allows limits to be set by the implementation so nothing has
actually changed w.r.t. conformance state.

Reported by Gustavo Grieco.

Fix proto in doc

Implemented json_pack() format specifiers 's?', 'o?', and 'O?'.

Fix libdir is wrong path when compile with cmake

Optimized functions

because JANSSON_INSTALL_LIB_DIR is set to /usr/local/lib after
foreach loop

Optimized json_equal, json_delete, json_copy, json_deep_copy
Replaced if to switch
Removed unnecessary check for NULL.

It's shown in the front page of readthedocs/latest.

pack_unpack: List first unrecognized key in strict unpacking

Otherwise figuring out what's wrong with your JSON can be tricky,
especially if you're using a single fmt string to validate a large,
complicated schema.

The comma delimiting will make separating keys that contain commas
difficult.  For example:

  {"foo, bar": true, "baz": false}

will generate errors like:

  2 object item(s) left unpacked: foo, bar, baz

but that seems like a small enough corner case to not be worth much
worrying.

I wanted to find a way to handle this without have_unrecognized_keys,
but the strbuffer tooling makes it look like I shouldn't be reaching
in to do things like:

  strbuffer_t unrecognized_keys;
  unrecognized_keys.value = NULL;

and then using 'unrecognized_keys.value == NULL' in place of
have_unrecognized_keys.

Add json_get_alloc_funcs() to allow alloc function fetching

This is particularly useful in modular situations where the allocation
functions are either unknown or private. For instance, in such cases,
the caller of json_dumps() has no way to free the returned buffer.

Fixes #258

changed code from while to do/while

Improve usage of snprintf in dump.c

Be more explicit that a cast is happening.

Be more future proof by keeping the number of magic constants low.

Update test_memory_funcs.c

Buildable with MS Compiler version  >= 1900

Fixes #230.

Fixes #237.