Mention that libtoolize is needed if you're not using a release tarball.
Fix the _MSC_VER check so it compiles on non-windows compilers.  Issue#91
Issue#84: explicitly remove old headers and include/json directory so creating the compat symlink can work.
Eliminate use of MC_ABORT in json-c code, and mark MC_ABORT/mc_abort deprecated.
Also adjust an error message in json_util to make it unique.  Fixes #87.