DSXMENU non selectable info lines

[NebularNerd]

Closes #57

After many, many moons of leaving this issue open I've finally cracked it! This tiny upgrade for DSXMENU now allows for non selectable info lines. This is ideal for explaining the choices available e.g.: Sound options, Trainers, or simply a note like:

------------------------------------------------------
Type any answer to bypass manual check screen.
Save files are broken, use DOSBOX states!
------------------------------------------------------

The key difference is the .ini file uses a dummy __INFO__ choice which the code will simply skip over:

# example menu
[menu]
menumessage=Welcome to the Custom Boot Selector!
menuitem=__INFO__,--------------------------------------------------
menuitem=__INFO__,These __INFO__ lines cannot be selected or.
menuitem=__INFO__,highlighted, they are for adding little notes.
menuitem=__INFO__,--------------------------------------------------
menuitem=choice_a,Menu item A
menuitem=choice_b,Menu item B
menuitem=choice_c,Menu item C
menudefault=choice_b,10

# NTS: Common commands are executed before menu items
[common]
echo Common 1
echo Common 2

[choice_a]
# NTS: Unlike MS-DOS, these are autoexec.bat like commands
echo Choice A
echo Another choice A

[choice_b]
# NTS: Unlike MS-DOS, these are autoexec.bat like commands
echo Choice B
echo Another choice B

[choice_c]
# NTS: Unlike MS-DOS, these are autoexec.bat like commands
echo Choice C
echo Another choice C

command_008_reenc.mp4