Split error messages into separate files.

Update libbb.h, per suggestion from Vladimir, to include __attribute__((format
(printf ...))) stuff
 -Erik

libbb/Makefile

@@ -0,0 +1,11 @@
+# Silly wrapper makefile.  This Makefile is _not_ used by the build system for
+# busybox, it is just to make working on libbb more conveinient.
+#  -Erik Andersen
+
+all:
+	make -C .. libbb.a
+
+clean:
+	- rm -rf libbb.a
+	- find -name \*.o -exec rm -f {} \;
+