build: add README, COPYING, NEWS to dist

Make sure README, COPYING and NEWS are distributed in tarballs.
diff --git a/Makefile.am b/Makefile.am
index 18822be..79ea2e5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -9,7 +9,6 @@
 noinst_DATA =
 MANPAGES =
 CLEANFILES = $(BUILT_SOURCES)
-EXTRA_DIST =
 BUILT_SOURCES =
 
 GCC_COLORS ?= 'ooh, shiny!'
@@ -28,6 +27,11 @@
 AM_CPPFLAGS =
 AM_CFLAGS =
 
+EXTRA_DIST = \
+	README \
+	COPYING \
+	NEWS
+
 # ------------------------------------------------------------------------------
 # Version numbers