- Moved find_package() calls up to top directory so failure can occur
right away if any dependencies are missing
- Got rid of a bunch of header checks and preprocessor definitions that
aren't ever used; not sure why I had them there in the first place
- Renamed VERSION preprocessor definition to not conflict with Bro's.
- Removed check for HAVE_CONFIG_H; config.h will always be generated in the
binpac build directory, but if a parent directory has generated a config.h
and added that to compiler include search paths via include_directories(),
then that one should be used -- include_directories() appends paths by
default and the parent CMakeLists.txt will have called it first.
