tag/IcyMetadataParser: do not null-terminate strings in icy_parse_tag()

Just pass std::string_views into the unmodified buffer to
icy_parse_tag_item().

test/test_icy_parser.cxx

@@ -2,8 +2,6 @@
  * Unit tests for class IcyMetaDataParser.
  */
 
-#include "util/ScopeExit.hxx"
-
 /* include the .cxx file to get access to internal functions */
 #include "tag/IcyMetaDataParser.cxx"
 
@@ -16,13 +14,11 @@
 static std::unique_ptr<Tag>
 icy_parse_tag(const char *p)
 {
-	char *q = strdup(p);
-	AtScopeExit(q) { free(q); };
 	return icy_parse_tag(
 #ifdef HAVE_ICU_CONVERTER
 			     nullptr,
 #endif
-			     q, q + strlen(q));
+			     p, p + strlen(p));
 }
 
 static void