Add pkg-config support and deprecate cups-config

[michaelrsweet]

Most open source libraries now provide support for the pkg-config utility. This also handles the addition of external dependencies (GNU TLS, zlib, etc.) and reporting project-specific values like directories.

We should add a pkg-config file for CUPS ("cups.pc") that provides all of the current cups-config options, and then deprecate cups-config.

[surajkulriya]

hello @michaelrsweet
I have a query regarding this
with the help of .pc files we can support specific options like --libs, --cflags etc.
But there are few other options in cups-config like --serverbin, --serverroot that I guess we won't be able to support using .pc files. Although one thing that I noticed is that we rarely use such options.(--serverbin,--serverroot)
So will it be okay if in our new .pc file we add support of only options like --libs, --cflags that we use frequently.
Thanks

[michaelrsweet]

@surajkulriya The pkg-config command supports package-specific variables, e.g.:

pkg-config —variable=serverbin

to return the “serverbin” variable in the .pc file.