Remove iniparser from buxton

We no longer need to ship an internal copy of iniparser as it
already exist in software repositories of major distributions.

Sometimes iniparser is shipped without a .pc file, meaning we
need to manually check for the existence of the headers and
library, ensuring they'll work for Buxton.

Signed-off-by: Michael Ikey Doherty <michael.i.doherty@intel.com>