1. Remove reference to old $(LIGHTNINGD_OLD_LIB_OBJS) var (in handshaked too).
2. Make check depend directly on unit tests, insteadof weird lightningd/tests
variable.
3. check-source-bolt and check-whitespace are automatic for $(ALL_TEST_PROGRAMS)
so we don't need them here.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>