update glfw files with ifdef to get M_PI when using GCC

deps/glfw/examples/boing.c

@@ -30,6 +30,8 @@
 #if defined(_MSC_VER)
  // Make MS math.h define M_PI
  #define _USE_MATH_DEFINES
+#elif __GNUC__
+ #define _GNU_SOURCE
 #endif
 
 #include <stdio.h>

deps/glfw/examples/gears.c

@@ -24,6 +24,8 @@
 #if defined(_MSC_VER)
  // Make MS math.h define M_PI
  #define _USE_MATH_DEFINES
+#elif __GNUC__
+ #define _GNU_SOURCE
 #endif
 
 #include <math.h>

deps/glfw/examples/particles.c

@@ -27,6 +27,8 @@
 #if defined(_MSC_VER)
  // Make MS math.h define M_PI
  #define _USE_MATH_DEFINES
+#elif __GNUC__
+ #define _GNU_SOURCE
 #endif
 
 #include <stdlib.h>

deps/glfw/examples/splitview.c

@@ -9,15 +9,16 @@
 // (If the code seems a little bit strange here and there, it may be
 //  because I am not a friend of orthogonal projections)
 //========================================================================
-
-#define GLFW_INCLUDE_GLEXT
-#include <GLFW/glfw3.h>
-
 #if defined(_MSC_VER)
  // Make MS math.h define M_PI
  #define _USE_MATH_DEFINES
+#elif __GNUC__
+ #define _GNU_SOURCE
 #endif
 
+#define GLFW_INCLUDE_GLEXT
+#include <GLFW/glfw3.h>
+
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>

deps/glfw/examples/wave.c

@@ -11,6 +11,8 @@
 #if defined(_MSC_VER)
  // Make MS math.h define M_PI
  #define _USE_MATH_DEFINES
+#elif __GNUC__
+ #define _GNU_SOURCE
 #endif
 
 #include <stdio.h>

deps/glfw/tests/cursor.c

@@ -30,13 +30,15 @@
 //
 //========================================================================
 
-#include <GLFW/glfw3.h>
-
 #if defined(_MSC_VER)
  // Make MS math.h define M_PI
  #define _USE_MATH_DEFINES
+#elif __GNUC__
+ #define _GNU_SOURCE
 #endif
 
+#include <GLFW/glfw3.h>
+
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>