* NEWS: Remove AS_DIRNAME and AS_BASENAME, replacing them with

* NEWS: Remove AS_DIRNAME and AS_BASENAME, replacing them with
AS_VAR_SET_DIRNAME and AS_VAR_SET_BASENAME.
* doc/autoconf.texi (Programming in M4sh): Document this.  All uses
changed.  The newer interfaces are more reliable, as they allow
implementations that handle trailing newline correctly.  For now,
we're in a freeze, so I did not include the more-reliable
implementations, but I wanted to correct the interface before 2.60
goes out.
* lib/m4sugar/m4sh.m4 (_AS_DETECT_REQUIRED): Renamed from
AS_DETECT_REQUIRED.  All uses changed.
(_AS_DETECT_SUGGESTED): Renamed from AS_DETECT_SUGGESTED.
All uses changed.
(_AS_DETECT_BETTER_SHELL): Put ;; at the end of a case.
(_AS_BASENAME): Renamed from AS_BASENAME.  All uses changed.
Use "basename --" to protect against leading "-".
(_AS_BASENAME_EXPR): Renamed from AS_BASENAME_EXPR.  All uses changed.
(_AS_BASENAME_SED): Renamed from AS_BASENAME_SED.  All uses changed.
(_AS_BASENAME_PREPARE): Reject implementations that cannot handle "--".
(_AS_DIRNAME_PREPARE): Likewise.
(_AS_DIRNAME): Renamed from AS_DIRNAME.  All uses changed.
(_AS_DIRNAME_EXPR): Renamed from AS_DIRNAME_EXPR.  All uses changed.
(_AS_DIRNAME_SED): Renamed from AS_DIRNAME_SED.  All uses changed.
Use "dirname --".
(AS_VAR_SET_BASENAME, AS_VAR_SET_DIRNAME): New macros.
* tests/m4sh.at (AS_VAR_SET_DIRNAME): Renamed from AS_DIRNAME.
Test the new API.  Don't test internals, since they're probably
going to change anyway.
(AS_VAR_SET_BASENAME): Likewise, renamed from AS_BASENAME.

* bin/autoconf.as: Don't use AS_BASENAME or AS_DIRNAME.  This
removes a bootstrapping problem with the changes described above.
The AS_DIRNAME part wasn't used, anyway, and the AS_BASENAME
part can be done portably without all the deep Autoconf magic.