Don't use obsolete macros.

* autogen.sh: Warn about everything during autoreconf.
* configure.ac: Replaced obsolete macros with their modern counterparts.
* build/c_std.m4: Ditto.
* build/cxx.m4: Ditto.
* build/cxx_std.m4: Ditto.
* build/sun.m4: Ditto.
* build/macros.m4: Ditto. Removed all unused macros and renamed to...
* build/debug.m4: ...this, because only macro for debugging refcount has
left.
* build/glibmm_check_perl.m4: Deleted. None of the macros there was used.
* build/dk-feature.m4: Use AS_VAR_IF.
* Makefile.am: Removed distribution of deleted m4 file.