fix compilation in gcc

Makefile

@@ -4,7 +4,7 @@
 # the terms of the Do What The Fuck You Want To Public License, Version 2, as
 # published by Sam Hocevar. See the COPYING file for more details.
 
-CFLAGS = -g -Wall -Wextra -Werror
+CFLAGS = -g -Wall -Wextra -Werror -std=c99
 LDFLAGS = -lcheck
 
 all: scan-build test example

minmea.h

@@ -9,6 +9,8 @@
 #ifndef MINMEA_H
 #define MINMEA_H
 
+#define _BSD_SOURCE
+
 #ifdef __cplusplus
 extern "C" {
 #endif