[ng] rules: forbid old-fashioned suffix rules, prefer pattern rules

[ng] rules: forbid old-fashioned suffix rules, prefer pattern rules

Pattern rules are cleaner, safer, and vouched for in the GNU make manual
itself.  Supporting them instead of suffix rules will also allow us to
simplify a little the automake script, auxiliary perl modules, and
documentation.

This change introduces a slight backward-incompatibility now, in that
user provided definitions of the SUFFIXES variable or of the .SUFFIXES
target, as well as old-fashioned suffix rules, are now rejected.

Automake-NG still tries to parse and understand suffix-based pattern
rules though, to retain support for user-added file extensions in the
_SOURCES variables (see "Handling new file extensions" in the Automake
manual).

So, an usage like:

    SUFFIXES = .baz .c
    .baz.c:
            cp $< $@
    foo_SOURCES = foo.c bar.baz
    DISTCLEANFILES = bar.c

which was valid with mainline Automake, should be translated for
Automake-NG as:

    %.c: %.baz
            cp $< $@
    bin_PROGRAMS = foo
    foo_SOURCES = foo.c sub/bar.baz
    DISTCLEANFILES = bar.c

Note that suffix-based pattern rules with dot-less suffix are *not*
supported.

* NG-NEWS: Update.
* doc/automake.texi: Likewise.
* lib/am/footer.am: Declare '.SUFFIXES:' with empty dependencies, to
neutralize the default suffix rules.
* automake.in (&handle_footer): Reject the 'SUFFIXES' variable.  Don't
process its content anymore.  Don't generate the .SUFFIXES special target
anymore.
(&var_SUFFIXES_trigger): Remove.  And don't install it as an hook for the
now-deprecated 'SUFFIXES' variable.
* lib/Automake/Rule.pm (&define): Don't process old-fashioned suffix
rules specially, but just reject them.  Instead, process pattern rules
specially.
($_SUFFIX_RULE_PATTERN): Made local to the '&define' function, renaming
it as '$suffix_rule_rx'.
(&suffixes, @_suffixes): Delete, they are no more used.
(@EXPORT): Adjust.
(register_suffix_rule): Don't extend '@_suffixes' anymore.
(reset): Don't reset '@_suffixes' anymore.
* t/ext3.sh: Remove as obsolete.
* t/suffix4.sh: Likewise.
* t/suffix6.sh: Likewise.
* t/suffix6b.sh: Likewise.
* t/suffix7.sh: Likewise.
* t/suffix11.tap: Likewise.
* t/suffix6c.sh: Rename ...
* t/suffix-obj.sh: .. like this, and adjust.
* t/suffix-chain.tap: Rewrite a as "simple" test (rather than as
a TAP test), adjust, and rename ...
* t/suffix-chain.sh: ... like this.
* t/suffix3.tap: Likewise rewrite and rename ...
* t/suffix3.sh: ... like this.
* t/suffix8.tap: Likewise rewrite and rename ...
* t/suffix8.sh: ... like this.
* t/suffix10.tap: Likewise rewrite and rename ...
* t/suffix10.sh: ... like this.
* t/suffix5.sh: Adjust.
* t/suffix9.sh: Likewise.
* t/suffix13.sh: Likewise.
* t/parallel-tests8.sh: Likewise.
* t/warnings-strictness-interactions.sh: Likewise.
* t/warnings-win-over-strictness.sh: Likewise.
* t/warnings-precedence.sh: Likewise.
* t/warnings-override.sh: Likewise.
* t/warning-groups-win-over-strictness.sh: Likewise.
* t/amopts-variable-expansion.sh: Likewise.
* t/specflg10.sh: Likewise.
* t/suffix-rules-reject.sh: New test.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>