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/ifcparse/parse.cpp

@@ -134,7 +134,7 @@ std::string& spf_lexer<Reader>::get_temp_string() const {
 
 namespace {
 
-#if defined(__APPLE__)
+#if defined(__APPLE__) || defined(__EMSCRIPTEN__)
 double parse_double_c(const char* start, char** end) {
     static const locale_t loc = newlocale(LC_NUMERIC_MASK, "C", (locale_t)0);
     return strtod_l(start, end, loc);
@@ -154,11 +154,11 @@ bool parse_num_(const char* pStart, size_t size, T& val) {
         }
     }
     if constexpr (std::is_floating_point_v<T>) {
-#if defined(__APPLE__)
+#if defined(__APPLE__) || defined(__EMSCRIPTEN__)
         // pStart is NUL-terminated at pStart + size (callers pass c_str()), so
         // strtod_l stops exactly at the end of a well-formed number. from_chars
         // is not instantiated for double here — its float overload is =deleted
-        // in Apple's libc++.
+        // in libc++ (Apple's and Emscripten's).
         char* pEnd = nullptr;
         const double result = parse_double_c(pStart, &pEnd);
         if (pEnd != pStart + size) {