Also try to accomodate formats to explicitly exclude the decimal (e.g. %.0f).

json_object_private: Use unsigned 32-bit integer type for refcount

json_object: Avoid double free (and thus a segfault) when ref_count gets < 0

Makefile: Add ACLOCAL_AMFLAGS

Fix non-GNUC define for JSON_C_CONST_FUNCTION

This is recommended by the libtool manual.

json_object: Add size_t json_object_sizeof()

doc: Use other doxygen feature to specify mainpage

Previously a special tag was added to README.md to make this the
main page in Doxygen generated docs. When viewing the README on the
GitHub page this tag was not hidden.

After upgrading to Doxygen 1.8.8 (and above) in changeset
219025727d a new Doxygen feature can be
used to specify the main page: Since release 1.8.3 Doxygen has a special
option to set a markdown file as main page. When using this option we
can drop the tag, making the README rendered by GitHub nice to look at.

Fixes: ae66b24369

Also, add a table of contents, and a brief section on using json-c with links to
the header files most likely to be useful.

Fix a VS 2015 compiler warning.

In VS 2015, the warning text is "warning C4550: expression evaluates to a function which is missing an argument list".

Seems to perform better than outputting to string
and re-parsing it.

BENCHMARK - 1000000 iterations of 'dst2 = json_tokener_parse(json_object_get_string(src2))' took 20 seconds
BENCHMARK - 1000000 iterations of 'dst2 = json_tokener_parse(json_object_get_string(src2))' took 7 seconds

It should make a difference on embedded systems.
The test was performed on a i5 desktop CPU [~3.5 years of age].

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Because doing `json_tokener_parse(json_object_get_string(src))`
feels sloppy, dirty, and makes me want to cry at night
sometimes.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Issue #338, add json_object_add_int functions