This is because it's really easy to get a name collission if compiling
Jansson as a subproject in a larger CMake project. If one project includes
several subprojects each having their own config.h, this will cause the
wrong file to be loaded.
Added multiple CMake-related files to project.
Supports building the library and the tests.
See CMakeLists.txt for notes on how it works.
I had to adjust 3 existing files in order to disable some configuration
that should be taken care of by cmake/automake anyway.
I also added jansson.def from a future jansson version,
to test cmake's support for .def files (which works fine).
The decimal point '.' is changed to locale's decimal point
before/after JSON conversion to make C standard library's
locale-specific string conversion functions work correctly.
All the tests now call setlocale(LC_ALL, "") on startup to use the
locale set in the environment.
Fixes GH-32.
