[wip/genom3] Update to 2.99.22

Changes since 2.99.21:
 . Support an "extern" parameter in tcl procedure [$component types], returning
   the list of public types of the components interface.
 . Fix version in the genom3.pc file (use @PACKAGE_VERSION@ in instead of
   @VERSION@).
 . Install C client libraries and headers in a middleware-dependent location,
   so that multiple builds can be installed inside the same prefix. .pc files
   are "middlewarized" too, so PKG_CONFIG_PATH must be tuned.
 . Fix skeleton codels Makefile for -l c++ option.