Warnings about primary/prefix mismatch fixed and extended.

Warnings about primary/prefix mismatch fixed and extended.

* automake.in (%standard_prefix): Add `doc' and `locale'.
Rename `pkgdatadir' to `pkgdata'.  Similarly for`pkglibdir',
`pkgincludedir' and `pkglibexecdir'.
(handle_programs): List `pkglibexec', not `pkglib', among the
prefixes valid for the `PROGRAMS' primary.
(handle_data): List also `doc' among the prefixes valid for
the `DATA' primary.  This is required by automake's own build
system.
* tests/dirforbid.test: Test removed, superseded by ...
* tests/primary-prefix-invalid-couples.test: ... this new test.
* tests/primary-prefix-valid-couples.test: New test.
* tests/primary-prefix-documented-valid.test: Likewise.
* tests/primary-prefix-force-valid.test: Likewise.
* tests/java3.test: Adjusted, and extended a bit.
* tests/Makefile.am (TESTS): Updated.
* NEWS: Updated.

From a report by Eric Blake.