The get() API are sometimes nicer in C code because it's just simpler to
loop through C arrays, but they end up with similar API to the list()
variants for binding, or with a useless size return value (since most
higher level languages have length-aware array types, which is what
GList are transformed into).
So let's use the list() variants as the main ones and skip the get()
variants. I hesitated to rename the list() variants to get() with
`(rename-to)` annotations but since I am unsure if the get() bindings
are absolutely useless, I don't think it's the best idea. Maybe on some
other language usable as GI binding, the get() variant might be
different again and nicer to use. So if we shadowed these by renaming
list() ones, the day we change our mind, we'd have to rename get() ones
too (which would be very confusing), or else break bindings' API. To
avoid this, I just skip the get() ones altogether in bindings but leave
their name available in the bindings.
They only contain private functions and don't need to be installed or
included by gimp_pdb_headers.h.
The PDB generation part is done by adding a "lib_private" variable
that can be set on PDB groups which should not be public API; the rest
is manual Makefile fiddling.
It never belonged inside "tools". Also rename its "pdb" subdirectory
to "groups". This had to happen before 2.10 so cherry-picking between
branches doesn't become a nightmare in the future.