Fix compiler div-by-0 error when it encountered 1.0/0.0

with division by 0.
Tricked the compiler to use volatile local variable zero instead, so it
does not know for sure whether or not it's going to be zero.

to cJSON_ParseWithOpts, then that will store the error pointer (if
parsing fails).

thanks to kolman and Irwan Djajadi on SourceForge.

Using values in powers of two for cJSON_* constants

fixed segmentation fault for non-json input / provided test case

Publish the libraries and headers to the right directories during 'make install'.