Fix Windows (MSVC) and WASM (Emscripten) build failures

Both surfaced on the first Windows/WASM CI run of this branch:

- XmlSerializer.cpp: the IfcPropertySetDefinitionSet block used a C-style
  cast to convert the set to std::vector<IfcPropertySetDefinition>. GCC
  invokes the non-explicit conversion operator; MSVC rejects the cast to a
  template type (C2440/C3536/C2661). Use copy-initialisation instead, which
  invokes the same implicit conversion portably. (This block was dead until
  the SCHEMAS_->SCHEMA_HAS_ typo fix enabled it, so it had never hit MSVC.)

- parse.cpp: the floating-point parse path falls back to strtod_l because
  libc++ =deletes the float from_chars overload. That fallback was guarded
  for __APPLE__ only; Emscripten uses the same libc++, so WASM hit the
  deleted from_chars. Extend the guard to __EMSCRIPTEN__ (its musl provides
  strtod_l/newlocale, treating all locales as C).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/serializers/schema_dependent/XmlSerializer.cpp

@@ -300,7 +300,11 @@ ptree* descend(::logger& log, ifcopenshell::geometry::abstract_mapping* mapping,
 			(log, object, &IfcSchema::IfcObject::IsDefinedBy, &IfcSchema::IfcRelDefinesByProperties::RelatingPropertyDefinition);
 
 		for (auto& s : property_set_sets) {
-            auto set_sets_value = (decltype(property_sets))s;
+            // Copy-initialise (not a C-style cast) so the implicit
+            // IfcPropertySetDefinitionSet -> std::vector<IfcPropertySetDefinition>
+            // conversion operator is used. MSVC rejects the equivalent cast to a
+            // template type (C2440), whereas copy-initialisation is portable.
+            decltype(property_sets) set_sets_value = s;
             property_sets.insert(property_sets.end(), set_sets_value.begin(), set_sets_value.end());
 		}
 #endif