Define _POSIX_C_SOURCE

This allows using the default compiler defined by make(1) (i.e.,
c99(1)), thus improving POSIX compatibility.

Makefile

@@ -1,7 +1,6 @@
 .POSIX:
 .SUFFIXES: .c .o
 
-CC = cc # c99 (default value) does not allow POSIX extensions.
 PROJECT = slcl
 O = -Og
 CDEFS = -D_FILE_OFFSET_BITS=64 # Required for large file support on 32-bit.

handler.c

@@ -1,3 +1,5 @@
+#define _POSIX_C_SOURCE 200809L
+
 #include "handler.h"
 #include "http.h"
 #include "server.h"

html.c

@@ -1,3 +1,5 @@
+#define _POSIX_C_SOURCE 200809L
+
 #include "html.h"
 #include <dynstr.h>
 #include <errno.h>

http.c

@@ -1,3 +1,5 @@
+#define _POSIX_C_SOURCE 200809L
+
 #include "http.h"
 #include <dynstr.h>
 #include <sys/types.h>

main.c

@@ -1,3 +1,5 @@
+#define _POSIX_C_SOURCE 200809L
+
 #include "auth.h"
 #include "cftw.h"
 #include "handler.h"

page.c

@@ -1,3 +1,5 @@
+#define _POSIX_C_SOURCE 200809L
+
 #include "page.h"
 #include "http.h"
 #include "html.h"

server.c

@@ -1,3 +1,5 @@
+#define _POSIX_C_SOURCE 200809L
+
 #include "server.h"
 #include <fcntl.h>
 #include <sys/select.h>