build: Pass -Wall to automake in AM_INIT_AUTOMAKE

When we switched from the gnu to foreign flavor the warnings got more
lax, bring them up a notch.

configure.ac

@@ -11,7 +11,7 @@ AC_CONFIG_AUX_DIR([build-aux])
 
 AC_USE_SYSTEM_EXTENSIONS
 
-AM_INIT_AUTOMAKE([1.11 foreign nostdinc no-dist-gzip dist-xz])
+AM_INIT_AUTOMAKE([1.11 -Wall foreign nostdinc no-dist-gzip dist-xz])
 AM_SILENT_RULES([yes])
 
 AM_GNU_GETTEXT_VERSION([0.19])

debian/changelog

@@ -111,6 +111,7 @@ dpkg (1.18.0) UNRELEASED; urgency=low
     - Use single suffix rules instead of non-portable %-pattern rules.
     - Pass CC to the test suite, so that we can use a non-gcc compiler.
     - Call AM_PROG_AR to detect the correct system archiver to use.
+    - Pass -Wall to automake in AM_INIT_AUTOMAKE, not implied by foreign.
   * Packaging:
     - Remove old trigger related Breaks and Conflicts from dpkg.
     - Only use stackprotectorstrong when building dpkg with gcc >= 4.9.