Merge branch 'jk/no-common' into jch

Dev support to catch a tentative definition of a variable in our C
code as an error.

* jk/no-common:
  config.mak.dev: build with -fno-common

config.mak.dev

@@ -15,6 +15,7 @@ DEVELOPER_CFLAGS += -Wpointer-arith
 DEVELOPER_CFLAGS += -Wstrict-prototypes
 DEVELOPER_CFLAGS += -Wunused
 DEVELOPER_CFLAGS += -Wvla
+DEVELOPER_CFLAGS += -fno-common
 
 ifndef COMPILER_FEATURES
 COMPILER_FEATURES := $(shell ./detect-compiler $(CC))