Tune the definitions needed when building with -ansi.

The current definitions were mostly useful to glibc and followed its
feature_test_macros(3) documentation.

However, this means other platforms still had problems when building with
strict compilation flags. _BSD_SOURCE, for example, is only recognized by
glibc, and other platforms sometimes need _XOPEN_SOURCE instead, or even the
removal of some definitions (such as the outdate _POSIX_SOURCE one).

_POSIX_SOURCE also had to be conditionally defined in some places, as what
it enables or disables during compilation varies across systems.

common/vncauth.c

@@ -24,6 +24,7 @@
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
 #define _POSIX_SOURCE
+#define _XOPEN_SOURCE 600
 #endif
 #ifdef LIBVNCSERVER_HAVE_SYS_TYPES_H
 #include <sys/types.h>

libvncclient/rfbproto.c

@@ -26,6 +26,7 @@
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
 #define _POSIX_SOURCE
+#define _XOPEN_SOURCE 600
 #endif
 #ifndef WIN32
 #include <unistd.h>

libvncclient/sockets.c

@@ -24,6 +24,11 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
+#ifdef __linux__
+/* Setting this on other systems hides definitions such as INADDR_LOOPBACK.
+ * The check should be for __GLIBC__ in fact. */
+# define _POSIX_SOURCE
+#endif
 #endif
 #include <unistd.h>
 #include <errno.h>

libvncserver/httpd.c

@@ -23,6 +23,11 @@
  *  USA.
  */
 
+#ifdef __STRICT_ANSI__
+#define _BSD_SOURCE
+#define _POSIX_SOURCE
+#endif
+
 #include <rfb/rfb.h>
 
 #include <ctype.h>

libvncserver/rfbserver.c

@@ -28,6 +28,8 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
+#define _POSIX_SOURCE
+#define _XOPEN_SOURCE 600
 #endif
 #include <string.h>
 #include <rfb/rfb.h>

libvncserver/sockets.c

@@ -43,7 +43,11 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
-#define _POSIX_SOURCE
+#ifdef __linux__
+/* Setting this on other systems hides definitions such as INADDR_LOOPBACK.
+ * The check should be for __GLIBC__ in fact. */
+# define _POSIX_SOURCE
+#endif
 #endif
 
 #include <rfb/rfb.h>

libvncserver/websockets.c

@@ -28,7 +28,6 @@
 
 #ifdef __STRICT_ANSI__
 #define _BSD_SOURCE
-#define _POSIX_SOURCE
 #endif
 
 #include <rfb/rfb.h>