Add ldisk.c32 Lua module

ldisk.c32 is a Lua module that provides information about disks to Lua scripts
The example script com32/lua/test/detect_disks.lua uses it to implement some-
thing akin to 'disk.c32'.

The name 'ldisk.c32' was chosen to avoid a name-clash with 'disk.c32'.
Merge pull request #1 from emmericp/ldisk-lua-module

Add ldisk.c32 Lua module