Add BEAST_EXPECT macro:

This macro is used in the unit test framework to assist in
reporting the file and line number of test failures.

test/http/detail/chunk_encode.cpp

@@ -71,7 +71,7 @@ public:
     {
         std::string s;
         encode(s, args...);
-        expect(s == answer);
+        BEAST_EXPECT(s == answer);
     }
 
     void run() override