compiler: -Wnested-externs hardening

configure.ac

@@ -710,6 +710,7 @@ AX_CHECK_COMPILE_FLAG([-fdiagnostics-show-option], [CFLAGS="$CFLAGS -fdiagnostic
 AX_CHECK_COMPILE_FLAG([-Werror=shift-count-overflow], [CFLAGS="$CFLAGS -Werror=shift-count-overflow"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Werror=shift-overflow=2], [CFLAGS="$CFLAGS -Werror=shift-overflow=2"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wdate-time], [CFLAGS="$CFLAGS -Wdate-time"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-Wnested-externs], [CFLAGS="$CFLAGS -Wnested-externs"],,[-Werror])
 
 AX_CHECK_LINK_FLAG([-z relro], [LDLAGS="$LDLAGS -z relro"],,[])
 AX_CHECK_LINK_FLAG([-z now], [LDLAGS="$LDLAGS -z now"],,[])

src/tests/lxc-test-utils.c

@@ -38,6 +38,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include "confile_utils.h"
 #include "lxctest.h"
 #include "macro.h"
 #include "utils.h"
@@ -519,8 +520,6 @@ void test_parse_byte_size_string(void)
 
 void test_lxc_config_net_hwaddr(void)
 {
-	bool lxc_config_net_hwaddr(const char *line);
-
 	if (!lxc_config_net_hwaddr("lxc.net.0.hwaddr = 00:16:3e:04:65:b8\n"))
 		exit(EXIT_FAILURE);