Summary of changes for v3.0.0:
- got tests working when RPATH is skipped
- made it work with system-installed suitesparse (using CXSparse)
- fixed up old Makefile-based build (not really useful but
 whatever.. alternative is to just remove it)
- got tests working under all combination of configurations
 (with/without merit functions, etc.)
- added a file for pkg-config
- added an option for install location of cmake files
- made it generate a new version of fclib.h with implementation
 stuff removed when HARDCODE_NOT_HEADER_ONLY is enabled -- the idea
 is that it is a normal library we just install in /usr/include and
 /usr/lib, so no need for weird header-only stuff to be even
 present in the packaged version.
- the generated header also defines FCLIB_WITH_MERIT_FUNCTIONS and
 FCLIB_NOT_HEADER_ONLY according to configuration.