* automake.in (handle_source_transform): If it's present, use

* automake.in (handle_source_transform): If it's present, use
libfoo_la.c instead of libfoo.c as the default source of
libfoo.la, and issue an -Wobsolete diagnostic.  Do not be
greedy in the suffix replacement regex.
* doc/automake.texi (Default _SOURCES): New node.
(Program Sources, Libtool Modules): Refer to it.
* tests/ltlibsrc.test: Update to check for old default source files.