lp1
lp2
Loop bug fixes

Check 'variable' slots have lvalues
better 'for' loop (RepeatControlBlock)
Better exception messages
Suggested name change to 'for' loop

Because this block silently does things for you that a 'for' loop in C++
expects you to handle - users may get confused as they progress to text
programming?

and 'increment' isn't the right english word for something that may be
decreasing.
bugfix

My shortcuts had stopped 'doubles' working correctly - still don't know
why.

This works OK.
Tiny Code a bit
tatting
Merge pull request #93 from TonyCallear/LoopBugFixesTNG

Loop bug fixes tng