Use cups library calls with explicit connection arguments in CupsPrinter methods.
Use connection attribute on CupsPrinter class in cups library calls.
Support printing to remote CUPS server.
Add short example for using remote cups server.
Support remote CUPS server in PPD lookup.
Use library path logic built into FFI.

The hardcoded library path lookup needed some fixing before. And it
still fails on a Ubuntu multiarch setup with both i368 and amd64 libcups
packages.

This reverts the library path lookup introduced in #3835be7a3e while
maintaining the possibility providing a CUPS_LIB using the environment.
Merge branch 'libcups-multiarch'
Merge pull request #9 from huerlisi/master

Support for remote CUPS server.  Library path cleanup.