Reduce the amount of time the framebuffer lock is held for

gl-natives/src/main/c/jaggl.c

@@ -343,11 +343,11 @@ static void *jaggl_proc_addr(const char *name) {
 		return;
 	}
 
-	[lock lock];
-
 	glClearColor(0, 0, 0, 1);
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
+	[lock lock];
+
 	if (framebuffer) {
 		glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, framebuffer);
 		glBlitFramebufferEXT(0, 0, framebuffer_width, framebuffer_height, 0, 0, framebuffer_width, framebuffer_height, GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT, GL_NEAREST);