Define _POSIX_C_SOURCE=200809L

This is needed to enable localtime_r(3) used in src/slog.c
Also needed for strdup(3)
Add #ifndef to src/hiredis/fmacros.h to avoid warnings

Makefile

@@ -5,7 +5,7 @@ B64_OBJS?=src/b64/cencode.o
 FORMAT_OBJS?=src/formats/json.o src/formats/raw.o src/formats/common.o src/formats/custom-type.o
 HTTP_PARSER_OBJS?=src/http-parser/http_parser.o
 
-CFLAGS ?= -std=c99 -Wall -Wextra -Isrc -Isrc/jansson/src -Isrc/http-parser -MD
+CFLAGS ?= -std=c99 -Wall -Wextra -Isrc -Isrc/jansson/src -Isrc/http-parser -MD -D_POSIX_C_SOURCE=200809L
 LDFLAGS ?= -levent -pthread
 
 # Pass preprocessor macros to the compile invocation

src/hiredis/fmacros.h

@@ -2,7 +2,9 @@
 #define __HIREDIS_FMACRO_H
 
 #define _XOPEN_SOURCE 600
+#ifndef _POSIX_C_SOURCE
 #define _POSIX_C_SOURCE 200112L
+#endif
 
 #if defined(__APPLE__) && defined(__MACH__)
 /* Enable TCP_KEEPALIVE */