make distcheck fixes

[libt2n] / example-codegen / TODO

multiple command groups test: howto multiplex multiple commands on one stream?
don't multiplex but a select on multiple groups would be nice

include problem:
- i don't see a solution using gccxml
- a simple solution would be to have a special include file containing the neccessary includes (or 2: one for the type definitions and one for the serialization)
- another solution would be to extract the includes from the file and add them to the generated code
both solutions only work if the include paths used during compilation of a program using the library are correct[tm]

now we use the first solution

- make distcheck
- .pc file
- make install (in this example the "other" client lib would have to install foo.hxx)
- test using valgrind
- would be nice to reduce amount of changed files
  (codegen output is often the same as the existing files - something similar to ccache
  for codegen - but not overwriting output files if they are the same)
- howto include the part after "# always the same:" in all makefiles using the codegenerator
- lib name should be group name + suffix/prefix