base64: Fixed compilation warnings when using Curl_base64_decode()

curl_sasl.c:294: warning: dereferencing type-punned pointer will break
strict-aliasing rules

getpart.c:201: warning: dereferencing type-punned pointer will break
strict-aliasing rules

lib/curl_sasl.c

@@ -286,12 +286,12 @@ CURLcode Curl_sasl_decode_digest_md5_message(const char *chlg64,
                                              char *alg, size_t alen)
 {
   CURLcode result = CURLE_OK;
-  char *chlg = NULL;
+  unsigned char *chlg = NULL;
   size_t chlglen = 0;
   size_t chlg64len = strlen(chlg64);
 
   if(chlg64len && *chlg64 != '=') {
-    result = Curl_base64_decode(chlg64, (unsigned char **) &chlg, &chlglen);
+    result = Curl_base64_decode(chlg64, &chlg, &chlglen);
     if(result)
       return result;
   }
@@ -301,19 +301,19 @@ CURLcode Curl_sasl_decode_digest_md5_message(const char *chlg64,
     return CURLE_BAD_CONTENT_ENCODING;
 
   /* Retrieve nonce string from the challenge */
-  if(!sasl_digest_get_key_value(chlg, "nonce=\"", nonce, nlen, '\"')) {
+  if(!sasl_digest_get_key_value((char *)chlg, "nonce=\"", nonce, nlen, '\"')) {
     Curl_safefree(chlg);
     return CURLE_BAD_CONTENT_ENCODING;
   }
 
   /* Retrieve realm string from the challenge */
-  if(!sasl_digest_get_key_value(chlg, "realm=\"", realm, rlen, '\"')) {
+  if(!sasl_digest_get_key_value((char *)chlg, "realm=\"", realm, rlen, '\"')) {
     /* Challenge does not have a realm, set empty string [RFC2831] page 6 */
     strcpy(realm, "");
   }
 
   /* Retrieve algorithm string from the challenge */
-  if(!sasl_digest_get_key_value(chlg, "algorithm=", alg, alen, ',')) {
+  if(!sasl_digest_get_key_value((char *)chlg, "algorithm=", alg, alen, ',')) {
     Curl_safefree(chlg);
     return CURLE_BAD_CONTENT_ENCODING;
   }

tests/server/getpart.c

@@ -191,14 +191,14 @@ static int decodedata(char  **buf,   /* dest buffer */
                       size_t *len)   /* dest buffer data length */
 {
   int error = 0;
-  char *buf64 = NULL;
+  unsigned char *buf64 = NULL;
   size_t src_len = 0;
 
   if(!*len)
     return GPE_OK;
 
   /* base64 decode the given buffer */
-  error = (int) Curl_base64_decode(*buf, (unsigned char **) &buf64, &src_len);
+  error = (int) Curl_base64_decode(*buf, &buf64, &src_len);
   if(error)
     return GPE_OUT_OF_MEMORY;