Remove unsafe package library

package.loadlib() can be used to load a dynamic C library allowing
arbitrary code execution in mod charts and themes.

So far I haven't found any theme that depends on the library, so I think
removing it shouldn't break anything.

Docs/Luadoc/Lua.xml

@@ -271,7 +271,6 @@
 		<Function name='rec_count_children'/>
 		<Function name='rec_print_children'/>
 		<Function name='rec_print_table'/>
-		<Function name='require'/>
 		<Function name='round'/>
 		<Function name='scale'/>
 		<Function name='scale_to_fit'/>

Docs/Luadoc/LuaDocumentation.xml

@@ -580,10 +580,6 @@ save yourself some time, copy this for undocumented things:
 	<Function name='ReportStyle' return='void' arguments=''>
 		Sends the current style to the server.
 	</Function>
-	<Function name='require' return='void' arguments='string modname'>
-		Loads the specified module.<br />
-		<code>require</code> is a core function of Lua's basic library; see the Lua manual for more details.
-	</Function>
 	<Function name='round' theme='_fallback' return='int' arguments='float val, int decimal'>
 		[02 Utilities.lua] Round a number.
 	</Function>