news: YYERROR vs variants
reports: display %empty in the generated pointed-rules

* src/print.c (print_core): Use %empty for empty rules.
* src/print_graph.c (print_core): Ditto.
* tests/conflicts.at, tests/output.at, tests/reduce.at: Adjust
expectations.
xml: also display %empty for empty right-hand sides

* data/xslt/xml2dot.xsl, data/xslt/xml2text.xsl: Display %empty where needed.
style: formatting changes

* src/print-xml.c: here.
xml: also use "%empty" with html output

* data/xslt/xml2xhtml.xsl: No longer issue an Epsilon, display as in
dot and text formats.
output: do not generate source files when early errors are caught

Reported by Alexandre Duret-Lutz as "second problem" in:
http://lists.gnu.org/archive/html/bug-bison/2013-09/msg00015.html

One problem is that some errors are caught early, before the
generation of output files, while others can only be detected
afterwards (since, for instance, skeletons can raise errors
themselves).

This will be addressed in two steps: early errors do not generate
source files at all, while later errors will remove the files that
have already been generated.

* src/scan-skel.l (yyout): Open to /dev/null when there are errors.
* tests/output.at (AT_CHECK_FILES): Factored out of...
(AT_CHECK_OUTPUT): this.
Fuse the "SHELLIO" argument in the "FLAGS" one.
Use $5 to denote the expected exit status.
Add a test case for early errors.
output: record what generated files are source or report files

* src/files.h, src/files.c (output_file_name_check): Take an additional
argument to record whether a file is a source or report file.
* src/files.c (generated_file): New.
(file_names, file_names_count): Replace with...
(generated_files, generated_files_size): these.
* src/scan-skel.l: Adjust.
output: do not generate source files when late errors are caught

Reported by Alexandre Duret-Lutz as "second problem" in:
http://lists.gnu.org/archive/html/bug-bison/2013-09/msg00015.html

* bootstrap.conf: We need the "unlink" module.
* src/files.h, src/files.c (unlink_generated_sources): New.
* src/output.c: Use it.
* tests/output.at: Check the case of late errors.
gnulib: update

* gnulib: here.
version 3.0.2

* NEWS: Record release date.
maint: post-release administrivia

* NEWS: Add header line for next release.
* .prev-version: Record previous version.
* cfg.mk (old_NEWS_hash): Auto-update.