module to check availability of a library for FFI

 FFI::CheckLib checks whether a particular dynamic library is available for
 FFI to use. It is modeled heavily on Devel::CheckLib, but will find dynamic
 libraries even when development packages are not installed. It also provides
 a find_lib function that will return the full path to the found dynamic
 library, which can be feed directly into FFI::Platypus or FFI::Raw.
 .
 Although intended mainly for FFI modules via FFI::Platypus and similar, this
 module does not actually use any FFI to do its detection and probing.