* 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.