HEADS UP: Forth Optimizations

[Devin Teske]

Hi Everybody,

Adrian (my co-mentor) wanted some additional eyes/names for review on a patch I'm making to sys/boot/forth (patch attached as patch.txt).

The patch makes no changes to user experience or functionality (but _does_ fix one incident of stack leakage -- among other things).

I wrote/tested this over a 2-day period using (as usual) VMware. I booted up several times (10+) and fiddled with many things (twiddled every knob, dropped to the loader prompt and went back to the menu several times, tried throwing various options like boot_single="YES" and boot_verbose="YES" into loader.conf(5) to make sure dynamic initialization is still working etc.).

The only thing I noticed after applying the patch was a drop in heap usage (one of the goals of the patch), showing that the optimizations did their job to make a leaner running menu. Also, the code is a lot more readable and got slightly reduced in size during the process.

Can someone help review this for the commit log?
-- 
Devin

===

+ This patch does not change user experience or functionality
+ Cleanup syntax, slim-down code, and make things more readable
+ Introduce new +c! operator and ilk to reduce heap usage/allocations
+ Fix a stack leak in [unused] cycle_menuitem function while we're here
 (required misconfiguration and/or missing environment vars to occur)
+ Add safemode_enabled? safemode_enable and safemode_disable functions
+ Add singleuser_enabled? singleuser_enable singleuser_disable functions
+ Add verbose_enabled? verbose_enable and verbose_disable functions
+ Centralize strings (also to reduce heap usage)

PR:
Submitted by:
Reviewed by:    Your_Name_Here, adrian (co-mentor) [pending his/your review]
Approved by:    adrian (co-mentor) [pending his approval]
Obtained from:
MFC after:
Security:
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> Reviewed by:   If someone else reviewed your modification.
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> MFC after:     N [day[s]|week[s]|month[s]].  Request a reminder email.
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M    forth/menu-commands.4th
M    forth/menu.4th

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