libsaria: Added function for getting the library size

I like to show this on the library tab so I know how many songs are
currently in the library.

include/libsaria/library.h

@@ -18,6 +18,8 @@ namespace libsaria
 		void add_path(string);
 		void play_id(ino_t);
 		void for_each(void (*)(Track &));
+
+		unsigned int size();
 	}
 }
 

libsaria/library/library.cpp

@@ -63,6 +63,15 @@ namespace libsaria
 		}
 	}
 
+	unsigned int library::size()
+	{
+		unsigned int size = 0;
+		map<string, LibraryPath>::iterator it;
+		for (it = path_map.begin(); it != path_map.end(); it++)
+			size += it->second.size();
+		return size;
+	}
+
 	void library::refresh()
 	{
 		trigger_callback(LIBRARY_REFRESH);