Avoided enabling openGL 3 support on linux, which was causing problems because of missing symbols.

modules/juce_opengl/juce_opengl.h

@@ -63,18 +63,19 @@
  #endif
 #elif JUCE_MAC
  #if defined (MAC_OS_X_VERSION_10_7) && (MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_7)
+  #define JUCE_OPENGL3 1
   #include <OpenGL/gl3.h>
   #include <OpenGL/gl3ext.h>
  #else
   #include <OpenGL/gl.h>
-  #include "OpenGL/glext.h"
+  #include <OpenGL/glext.h>
  #endif
 #elif JUCE_ANDROID
  #include <GLES2/gl2.h>
 #endif
 
-#if GL_VERSION_3_2 || GL_ES_VERSION_3_0
- #define JUCE_OPENGL3  1
+#if GL_ES_VERSION_3_0
+ #define JUCE_OPENGL3 1
 #endif
 
 //=============================================================================