Fix building error.c on Windows.

src/libespeak-ng/error.c

 		strncpy0(buffer, "The phoneme manifest file does not contain any phonemes", length);
 		break;
 	default:
-		if ((status & ENS_GROUP_MASK) == ENS_GROUP_ERRNO)
+		if ((status & ENS_GROUP_MASK) == ENS_GROUP_ERRNO) {
+#ifdef PLATFORM_WINDOWS
+			strerror_s(buffer, length, status);
+#else
 			strerror_r(status, buffer, length);
-		else {
+#endif
+		} else {
 #ifdef PLATFORM_WINDOWS
 			sprintf(buffer, "Unspecified error 0x%x", status);
 #else