util/SplitString: convert return value to std::string_view

Eliminates lots of overhead.

src/lib/upnp/ContentDirectoryService.cxx

@@ -23,7 +23,7 @@
 #include "ixmlwrap.hxx"
 #include "util/UriRelative.hxx"
 #include "util/RuntimeError.hxx"
-#include "util/SplitString.hxx"
+#include "util/IterableSplitString.hxx"
 
 #include <upnptools.h>
 
@@ -73,5 +73,8 @@ ContentDirectoryService::getSearchCapabilities(UpnpClient_Handle hdl) const
 		   understand that */
 		return std::forward_list<std::string>();
 
-	return SplitString(s, ',', false);
+	std::forward_list<std::string> result;
+	for (const auto &i : IterableSplitString(s, ','))
+		result.emplace_front(i);
+	return result;
 }

src/lib/upnp/Discovery.cxx

@@ -325,7 +325,7 @@ UPnPDeviceDirectory::GetDirectories()
 }
 
 ContentDirectoryService
-UPnPDeviceDirectory::GetServer(const char *friendly_name)
+UPnPDeviceDirectory::GetServer(std::string_view friendly_name)
 {
 	const std::lock_guard<Mutex> protect(mutex);
 

src/lib/upnp/Discovery.hxx

@@ -176,7 +176,7 @@ public:
 	/**
 	 * Get server by friendly name.
 	 */
-	ContentDirectoryService GetServer(const char *friendly_name);
+	ContentDirectoryService GetServer(std::string_view friendly_name);
 
 private:
 	void Search();