Rewrite paperinfo in Perl plus a small C program localepaper.

As a result, none of the original code remains, so bump the license to
GPLv3+.

Because we only have a trivial C program, remove the requirement for
C99, and the GCC warnings apparatus from configure.ac.

Adjust make syntax-check exclusions.
Add a per-user paperspecs file.

Fix incorrect definition of paperspecs, transposed from previous
man-page's definition of run-parts scripts.
Don't need to use AC_PROG_INSTALL any more
Remove unnecessary whitespace.
Switch paperspecs format to CSV, and allow spaces in paper names.
Rename paperinfo to paper, and clarify the structure of the package.
Add more sizes, and add spaces to size names.