Much redundancy is removed from package scripts with this system.
It also supports simple dependency management, uninstalling (through
BSD ports style plist files), cleaning up after itself (with clean,
clean_dist, clean_all commands), etc.
This is a very basic mbedtls port. I've disabled the networking bits,
since they want some macros that we don't have defined. We might not even
want the networking functions anyway, since they wouldn't play very nice
with CEventLoop and friends.
