ui: shader.h protect against double inclusion

Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

include/ui/shader.h

+#ifndef QEMU_SHADER_H
+#define QEMU_SHADER_H
+
 #include <epoxy/gl.h>
 
 void qemu_gl_run_texture_blit(GLint texture_blit_prog);
@@ -6,3 +9,5 @@ GLuint qemu_gl_create_compile_shader(GLenum type, const GLchar *src);
 GLuint qemu_gl_create_link_program(GLuint vert, GLuint frag);
 GLuint qemu_gl_create_compile_link_program(const GLchar *vert_src,
                                            const GLchar *frag_src);
+
+#endif /* QEMU_SHADER_H */