Added GetNumLockedSongs() Lua binding.

This gets the number of songs that are locked for any reason.

I wonder why the unlocked songs functions say that songs locked
by unlock entries are counted there, but fair enough.

Docs/Changelog_sm5.txt

@@ -8,6 +8,10 @@ ________________________________________________________________________________
 StepMania 5.0 $next | 2011????
 --------------------------------------------------------------------------------
 
+2011/09/16
+----------
+* [UnlockManager] Added GetNumLockedSongs() Lua binding. [Wolfman2000]
+
 2011/09/12
 ----------
 * [NotesLoaderSSC/WriterSSC] Allow all timing tags regardless of what timing

Docs/Luadoc/Lua.xml

@@ -1330,6 +1330,7 @@
 			<Function name='GetNumAdditionalSongs'/>
 			<Function name='GetNumCourseGroups'/>
 			<Function name='GetNumCourses'/>
+			<Function name='GetNumLockedSongs'/>
 			<Function name='GetNumSelectableAndUnlockedSongs'/>
 			<Function name='GetNumSongGroups'/>
 			<Function name='GetNumSongs'/>

Docs/Luadoc/LuaDocumentation.xml

@@ -3513,6 +3513,9 @@
 	<Function name='GetNumSongs' return='int' arguments=''>
 		Returns the number of songs.
 	</Function>
+	<Function name='GetNumLockedSongs' return='int' arguments=''>
+		Returns the number of locked songs, regardless of reason for locking.
+	</Function>
 	<Function name='GetNumUnlockedSongs' return='int' arguments=''>
 		Returns the number of unlocked songs.
 	</Function>