GL: Disable scissor before FB blit.

src/renderer_gl.cpp

@@ -669,6 +669,7 @@ namespace bgfx
 #if BGFX_CONFIG_RENDERER_OPENGL|BGFX_CONFIG_RENDERER_OPENGLES3
 			if (0 != m_msaaBackBufferFbo)
 			{
+				GL_CHECK(glDisable(GL_SCISSOR_TEST) );
 				GL_CHECK(glBindFramebuffer(GL_FRAMEBUFFER, m_backBufferFbo) );
 				GL_CHECK(glBindFramebuffer(GL_READ_FRAMEBUFFER, m_msaaBackBufferFbo) );
 				GL_CHECK(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0) );