converters/utf8proc: Add support for pkg-config, Reduce build dependencies

- Drop cmake
  Drive libtool directly (utf8proc can be build with a single compiler call).
  This removes the C++11 build dependency for cmake (C99 is now sufficient)
  and more build dependencies that are at least an order of magnitude larger
  than utf8proc itself.
- Drop patch for cmake
- Add support for pkg-config
  Install "libutf8proc.pc".
- Bump PKGREVISION for additional installed files.
- Remove supported Unicode version from DESCR
  Was not maintained in the past
- Take maintainership

OK from minskim@
OK from wiz@ (as long as I am MAINTAINER)

(micha)