Fix building of GLSL demos which use M_PI
Some <math.h> files do not define M_PI, in which case, provide our own definition
Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
diff --git a/progs/glsl/texaaline.c b/progs/glsl/texaaline.c
index 7a5ac40..2e4f932 100644
--- a/progs/glsl/texaaline.c
+++ b/progs/glsl/texaaline.c
@@ -14,6 +14,9 @@
#include <GL/glew.h>
#include <GL/glut.h>
+#ifndef M_PI
+#define M_PI 3.1415926535
+#endif
static GLint WinWidth = 300, WinHeight = 300;
static GLint win = 0;