opencascade 7.8.1

Additionally modify the opencascade test to use C++ 11, as this is (or more recent)
is required by recent versions of opencascade

Formula/o/opencascade.rb

@@ -1,11 +1,10 @@
 class Opencascade < Formula
   desc "3D modeling and numerical simulation software for CAD/CAM/CAE"
   homepage "https://dev.opencascade.org/"
-  url "https://git.dev.opencascade.org/gitweb/?p=occt.git;a=snapshot;h=refs/tags/V7_7_2;sf=tgz"
-  version "7.7.2"
-  sha256 "2fb23c8d67a7b72061b4f7a6875861e17d412d524527b2a96151ead1d9cfa2c1"
+  url "https://git.dev.opencascade.org/gitweb/?p=occt.git;a=snapshot;h=refs/tags/V7_8_1;sf=tgz"
+  version "7.8.1"
+  sha256 "33f2bdb67e3f6ae469f3fa816cfba34529a23a9cb736bf98a32b203d8531c523"
   license "LGPL-2.1-only"
-  revision 4
 
   # The first-party download page (https://dev.opencascade.org/release)
   # references version 7.5.0 and hasn't been updated for later maintenance
@@ -113,6 +112,7 @@ def install
     # Make sure hardcoded library name references in our CMake config files are valid.
     (testpath/"CMakeLists.txt").write <<~CMAKE
       cmake_minimum_required(VERSION 3.5)
+      set(CMAKE_CXX_STANDARD 11)
       project(test LANGUAGES CXX)
       find_package(OpenCASCADE REQUIRED)
       add_executable(test main.cpp)