Fix PKCS#11 URI detection to be case insensitive

The RFC 7512 defines the URI scheme "pkcs11". As defined in RFC 3986,
URI schemes are case-insensitive, although the canonical form must be
written in lowercase. The RFC 4395 requires URI schemes names to be
registered using lowecase letters.

lib/vtls/openssl.c

@@ -538,7 +538,7 @@ static int ssl_ui_writer(UI *ui, UI_STRING *uis)
  */
 static bool is_pkcs11_uri(const char *string)
 {
-  if(!strncmp(string, "pkcs11:", 7)) {
+  if(strncasecompare(string, "pkcs11:", 7)) {
     return TRUE;
   }
   else {

src/tool_getparam.c

@@ -337,7 +337,7 @@ void parse_cert_parameter(const char *cert_parameter,
    * looks like a RFC7512 PKCS#11 URI which can be used as-is.
    * Also if cert_parameter contains no colon nor backslash, this
    * means no passphrase was given and no characters escaped */
-  if(!strncmp(cert_parameter, "pkcs11:", 7) ||
+  if(!curl_strnequal(cert_parameter, "pkcs11:", 7) ||
      !strpbrk(cert_parameter, ":\\")) {
     *certname = strdup(cert_parameter);
     return;

src/tool_operate.c

@@ -118,7 +118,7 @@ static bool is_fatal_error(CURLcode code)
  */
 static bool is_pkcs11_uri(const char *string)
 {
-  if(!strncmp(string, "pkcs11:", 7)) {
+  if(curl_strnequal(string, "pkcs11:", 7)) {
     return TRUE;
   }
   else {