Earlier we added "-Wformat-security" to developer builds, assuming
that "-Wall" (which includes "-Wformat" which in turn is required
to use "-Wformat-security") is always in effect. This is not true
when config.mak.autogen is in use, unfortunately. This has been
fixed by unconditionally adding "-Wall" to developer builds.
* jk/dev-build-format-security:
config.mak.dev: add -Wall, primarily for -Wformat, to help autoconf users