Revert "Use intermOut.cpp's IsNan and IsInfinity for parse-time constant folding"

glslang/MachineIndependent/intermOut.cpp

@@ -48,6 +48,37 @@
 #endif
 #include <cstdint>
 
+namespace {
+
+bool IsInfinity(double x) {
+#ifdef _MSC_VER
+    switch (_fpclass(x)) {
+    case _FPCLASS_NINF:
+    case _FPCLASS_PINF:
+        return true;
+    default:
+        return false;
+    }
+#else
+    return std::isinf(x);
+#endif
+}
+
+bool IsNan(double x) {
+#ifdef _MSC_VER
+    switch (_fpclass(x)) {
+    case _FPCLASS_SNAN:
+    case _FPCLASS_QNAN:
+        return true;
+    default:
+        return false;
+    }
+#else
+  return std::isnan(x);
+#endif
+}
+
+}
 
 namespace glslang {