Revert "[moar-gdb.py] attempt at using unicode box symbols"

This reverts commit 941000b2f9c306448fb06906e502bda121e13eb8.

gdb insists that our terminal can only do ascii.
[moar-gdb.py] MVMString isn't null-terminated
[moar-gdb.py] don't explode due to encoding
[moar-gdb.py] hooray for no coercive operators!
[moar-gdb.py] count strings in the string histogram
[moar-gdb.py] string histograms end up being really long.
[moar-gdb.py] analyze objects in the overflow