Extension uninstall issue with PGXS

Hi all,

I am in trouble when building an extension with PGXS. At uninstall time,
the documentation and script files are not removed.

The specificity of my distribution tree is that these script and
documentation files are located into subdirectories. So in the Makefile,
the DOCS and SCRIPTS variables are described like DATA, with something like:
DOCS         = \$(wildcard doc/*)
SCRIPTS      = \$(wildcard script/*)

At install time, all files of both subdirectories are correctly copied
into the DOCDIR and BINDIR directories respectively.
But at uninstall time, these files are not removed.

Attached is a simple test case that reproduces the issue, with the
execution result on my PC.

As you can see, the uninstall step tries to remove files from DOCDIR and
BINDIR, using the original subdirectories.

I don't know if this can be considered as a bug or if it is a functional
limitation or if there is a better way to code the Makefile.

Kind regards. Philippe.