Conv from UTF-8 to ASCII

`file *.c` to see file types (ASCII or UTF-8), convert UTF-8 (with BOM) to ASCII

```sh
sed '1s/^\xEF\xBB\xBF//'  sm4.c | iconv -f UTF-8 -t ASCII//TRANSLIT > temp.c
mv temp.c sm4.c
```

include/gmssl/pkcs8.h

@@ -1,4 +1,4 @@
-/*
+/*
  *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
  *
  *  Licensed under the Apache License, Version 2.0 (the License); you may
@@ -34,7 +34,7 @@ PBKDF2-params ::= SEQUENCE {
 		otherSource	AlgorithmIdentifier {{PBKDF2-SaltSources}}
 	},
 	iterationCount		INTEGER (1..MAX),
-	keyLength		INTEGER (1..MAX) OPTIONAL, -- 这个参数可以由函数指定
+	keyLength		INTEGER (1..MAX) OPTIONAL,
 	prf			AlgorithmIdentifier {{PBKDF2-PRFs}} DEFAULT algid-hmacWithSHA1
 }