Merge branch 'jk/struct-zero-init-with-older-gcc' into maint

Older gcc with -Wall complains about the universal zero initializer
"struct s = { 0 };" idiom, which makes developers' lives
inconvenient (as -Werror is enabled by DEVELOPER=YesPlease).  The
build procedure has been tweaked to help these compilers.
source: <YuQ60ZUPBHAVETD7@coredump.intra.peff.net>

* jk/struct-zero-init-with-older-gcc:
  config.mak.dev: squelch -Wno-missing-braces for older gcc