Use "" instead of <> for inter-project includes.

src/OpenGL.h

@@ -33,7 +33,7 @@
 
 /* Desktop OpenGL */
 #ifndef MAGNUM_TARGET_GLES
-    #include <OpenGL/GL/gl_magnum.h>
+    #include "OpenGL/GL/gl_magnum.h"
 
 /* NaCl has its own gl2.h, the official one causes linker issues. Additionaly
    to NaCl's gl2ext.h we are including our own to prevent undeclared symbol
@@ -45,19 +45,19 @@
     #include <GLES2/gl2.h>
     #include <GLES2/gl2ext.h>
     #undef __gl2ext_h_
-    #include <OpenGL/GLES2/gl2ext.h>
+    #include "OpenGL/GLES2/gl2ext.h"
 
 /* Generic OpenGL ES */
 #else
-    #include <OpenGL/KHR/khrplatform.h>
+    #include "OpenGL/KHR/khrplatform.h"
     #ifndef MAGNUM_TARGET_GLES2
-        #include <OpenGL/GLES3/gl3platform.h>
-        #include <OpenGL/GLES3/gl3.h>
+        #include "OpenGL/GLES3/gl3platform.h"
+        #include "OpenGL/GLES3/gl3.h"
     #else
-        #include <OpenGL/GLES2/gl2platform.h>
-        #include <OpenGL/GLES2/gl2.h>
+        #include "OpenGL/GLES2/gl2platform.h"
+        #include "OpenGL/GLES2/gl2.h"
     #endif
-    #include <OpenGL/GLES2/gl2ext.h>
+    #include "OpenGL/GLES2/gl2ext.h"
 #endif
 
 #endif