autotools: Simple changes for uniformity

Add build-aux and m4 directories so libtool can be vendored correctly
when doing a dist. Also reference the m4 directory from the automake
script to silence any warnings by autoreconf. Add verbose and force
flags to autoreconf to make sure it regenerates everything and gives us
useful feedback about where it is in the process.

Change-Id: I8ea5184d1ae4098c2122d3e4043128b6731f7e87
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/Makefile.am b/Makefile.am
index 9bcba6d..0129c2b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,3 +1,5 @@
+ACLOCAL_AMFLAGS = -Im4
+
 if WANT_LIBSDBUSPLUS
 
 nobase_include_HEADERS = \