Speed up GUID equality comparison.

libgnucash/engine/guid.cpp

@@ -412,9 +412,7 @@ GUID::operator < (GUID const & other) noexcept
 
 bool operator == (GUID const & lhs, GncGUID const & rhs) noexcept
 {
-    auto ret = std::mismatch (lhs.begin (), lhs.end (), rhs.reserved);
-    return ret.first == lhs.end ();
-
+    return lhs.implementation == GUID(rhs).implementation;
 }
 
 bool

libgnucash/engine/guid.hpp

@@ -55,6 +55,7 @@ struct GUID
     auto begin () const noexcept -> decltype (implementation.begin ());
     auto end () const noexcept -> decltype (implementation.end ());
     bool operator < (GUID const &) noexcept;
+    friend bool operator == (GUID const &, GncGUID const &) noexcept;
     friend bool operator != (GUID const &, GUID const &) noexcept;
 };